Washington (CNN) - The war of words over how the U.S. should approach potential military strikes in Syria will only intensify in the coming days as President Barack Obama asks Congress to officially weigh in.
After he and top officials in his administration outlined evidence behind their claim that Syrian President Bashar al-Assad was responsible for a chemical attack that killed 1,400 and injured 3,000 earlier this month, Obama's call Saturday for congressional authorization to strike Syria surprised Washington but was applauded by members on both sides of the aisle.
Some, however, questioned what would happen in the turbulent country in the week before Congress returns from its August recess on September 9.
Several Senate Democrats on the Foreign Relations and Armed Services committees pushed on a Friday conference call with administration officials for Obama to formally consult them.
And more than 160 House members – including 98 Republicans and 63 Democrats – signed letters to Obama asking that make his case before them.
They pointed to his responsibilities under the 1970s-era War Powers Resolution that attempted to resolve sometimes conflicting constitutional provisions assigning the president commander-in-chief powers and Congress the authority to declare war.
"While the founders wisely gave the office of the president the authority to act in emergencies, they foresaw the need to ensure public debate – and the active engagement of Congress – prior to committing U.S. military assets," one such letter read. "Engaging our military in Syria when no direct threat to the United States exists and without prior congressional authorization would violate the separation of powers that is clearly delineated in the Constitution."
They sharply criticized as unconstitutional Obama's decision not to seek authorization before the 2011 U.S. military action in Libya, which included airstrikes. In that case, Obama notified Congress of the military action but said the War Powers Resolution, which presidents since Richard Nixon have found ways to skirt, did not apply in that case because the U.S. was not engaged in "hostilities" as defined in the law.
A poll released Friday showed nearly eight in 10 Americans believed Obama should be required to receive congressional approval before taking any military action.
Debating national security interests
Foreign Relations Committee Chairman Robert Menendez said the evidence he has seen contains "no ambiguity" and that the "use of chemical weapons against the innocent brings us to a point of no return."
"We say what we mean, we mean what we say, and we don't look away when undeniable war crimes are committed. I will work with the Senate leadership in support of an authorization for use of military force as expeditiously as possible," he said.
But that administration's arguments for responding to the August 21 attack they say was perpetrated by al-Assad's forces aren't accepted by all on Capitol Hill. The administration contends the Syrian regime used chemical weapons, while al-Assad's government has blamed jihadists fighting with rebels.
Sen. Ted Cruz, a Texas Republican who sits on the Armed Services Committee, said he was pleased by Obama's decision, which is a sign that Obama "agrees that there is no imminent threat" to the U.S. national security.
"It is incumbent on the president to make the case that military action is in furtherance of the vital national security interest of the United States," he told reporters after speaking to a conservative gathering in Florida. "I am troubled by the justifications the Obama administration has put forth so far.
"Much of their discussion has concerned what they describe as international norms and they have suggested that the U.S. military should be employed to vindicate so-called international norms," he continued. "In my view, U.S. military force is justified only to protect the vital national security interest of the United States."
He is in the same camp as Sen. Rand Paul, a Kentucky Republican from the Foreign Relations Committee, who said little more in a statement than applaud Obama's move. But in an op-ed for CNN.com published Friday, he argued against U.S. intervention, saying, "it seems on all sides we have violence and chaos and it is unclear if any side will, in the end, be a friend of the United States."
Two top Senate Republicans – who have found themselves at odds with Paul and Cruz on other national security issues – repeated their call that airstrikes would not be enough.
Sens. John McCain and Lindsey Graham wrote in a joint statement, "Since the president is now seeking congressional support for this action, the Congress must act as soon as possible.
"However, we cannot in good conscience support isolated military strikes in Syria that are not part of an overall strategy that can change the momentum on the battlefield, achieve the president's stated goal of Assad's removal from power, and bring an end to this conflict, which is a growing threat to our national security interests," they wrote. "Anything short of this would be an inadequate response to the crimes against humanity that Assad and his forces are committing."
A third Republican - Sen. Ron Johnson of Wisconsin - appeared to concur, saying he would vote against an authorization if the administration planned only to make limited airstrikes.
"If that's all it is you're better off doing nothing and keeping them wondering what we would we do if we really got serious," Johnson told CNN.
How Obama's decision came about
Senior administration officials said Obama met with senior advisers Friday evening while wrestling with whether or not to formally consult Congress. He took a walk with his chief of staff, then asked for advice from Vice President Joe Biden, Secretary of State John Kerry and Defense Secretary Chuck Hagel, said the officials, who spoke to reporters on the condition of anonymity.
Missouri Republican Rep. Roy Blunt said Obama's decision was long overdue.
"After weeks of claiming he could and would make this decision on his own, the president's announcement today marks an astonishing change of course. While congressional approval is the best course of action and the right thing to do, it would have been the right course of action months ago."
And Senate Intelligence Committee vice-chairman Saxby Chambliss, a Republican from Georgia, said "the United States must respond" to the alleged chemical attack, but should have been called back early.
"He should have already presented Congress with a strategy and objectives for military action, including what impact this will have on our allies and enemies alike in the region," Chambliss said. "Leadership is about reacting to a crisis, and quickly making the hard and tough decisions. The president should have demanded Congress return immediately and debate this most serious issue."
At least three other members of the House and Senate also demanded Congress be called back early.
One Republican blasted Obama for "abdicating his responsibility as commander-in-chief and undermining the authority of future presidents.
"The president does not need Congress to authorize a strike on Syria," said Rep. Peter King of New York. "If Assad's use of chemical weapons against civilians deserves a military response, and I believe it does, and if the President is seeking congressional approval, then he should call Congress back into a special session at the earliest date. The president doesn't need 535 members of congress to enforce his own redline."
Senate Republican leader Mitch McConnell, however, said "the president's role as commander-in-chief is always strengthened when he enjoys the expressed support of the Congress."
The top Republican on the Senate Foreign Relations Committee, Bob Corker, said the request for congressional authorization "is absolutely the right decision, and I look forward to seeing what the administration brings forward and to a vigorous debate on this important authorization. Further, now that the president has decided to use force and seek authorization, it is imperative that he immediately begins using every ounce of his energy to make his case to the American people."
Obama's statement puts on hold military action that as recently as Saturday morning seemed like it could be imminent.
On Friday, Kerry detailed the administration's case against al-Assad in a methodically-constructed address at the State Department. Shortly after, Obama described himself and the country as "war-weary," but said his team was "looking at the possibility of a limited, narrow act that would help make sure that not only Syria, but others around the world, understand that the international community cares about maintaining this chemical weapons ban and norm."
United Nations investigators departed Syria early Saturday, and word of a series of congressional briefings emerged.
Senators were to be briefed on Saturday afternoon and again on Sunday, both times by phone. Boehner's office Sunday afternoon classified briefing for House members.
In the meantime
Following the statement, key members of Obama's national security team were to speak with Republican and Democratic members of the Senate in separate conference calls. Sources said the calls would include Secretary of State John Kerry, Defense Secretary Chuck Hagel, the Joint Chiefs of Staff Chairman Gen. Martin Dempsey, National Security Adviser Susan Rice and Director of National Intelligence James Clapper.
That call would be unclassified, apparently so the many members outside of Washington this Labor Day weekend could join from unsecure telephone lines.
One Republican senator on that call told CNN several senators on that call asked why the U.S. could wait for a vote, allowing Syria to prepare for possible airstrikes.
Administration officials said they could not answer those questions on the unsecured line, but would explain their comfort in waiting in a classified setting.
Senate Armed Services Committee Chairman Carl Levin said Obama "wisely chose to seek congressional support."
"I have again urged the president to use this time to help the Syrian people defend themselves by assisting vetted elements of the Syrian opposition in obtaining more effective weapons such as anti-tank weapons," Levin said in a statement.
After stepping away from the cameras, Obama and Biden changed out of their suits and went golfing.
– CNN's Dana Bash and Jim Acosta reported from Washington; Gregory Wallace reported and wrote; Barbara Starr, Jill Dougherty, Paul Steinhauser, Laura Bernardini, Lisa Desjardins, Ted Barrett, Jennifer Rizzo, and Gabriella Schwarz contributed.