Washington (CNN) - As the U.S. prepares for a possible military strike on Syria, more than three dozen lawmakers - among them a handful of Democrats - demanded the Obama administration consult them, saying taking action without congressional approval is unconstitutional.
"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," the 37 congressmen and women wrote to President Barack Obama on Tuesday. "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 said that the 2011 U.S. military action in Libya, which included airstrikes, was unconstitutional and set a bad precedent the Obama administration should not apply in this situation. 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.
But, the lawmakers argue that argument is rubbish. "If the use of 221 Tomahawk cruise missiles, 704 Joint Direct Attack Munitions, and 42 Predator Hellfire missiles expended in Libya does not constitute 'hostilities,' what does?" the letter reads. It's signatories include six Democrats and all are members of the House.
The White House continued on Tuesday to lay the groundwork for a military strike, including offering legal justification, following the August 21 suspected chemical attack that the U.S. blames on Syrian President Bashar al-Assad. Press Secretary Jay Carney insisted Obama had not yet made a decision on how to respond, but firmly said "there must be a response" to that alleged attack, which Syria denies.
While that government said rebel groups were responsible for chemical warfare, Vice President Joe Biden said Tuesday that Syrian government forces are "the only ones that have the weapons."
The administration has not said whether the scenarios they are preparing would fall under the War Powers Resolution, nor if they plan to seek congressional authorization for military force, which is required under the act within 60 days of hostilities beginning. Lawmakers are slated to return from their five-week summer recess next month but could be called back earlier.
Other members from both sides of the aisle urged the administration to release more information publicly. Carney said Monday military action would be preceded by the public release of a U.S. intelligence report on the incident. That report is expected this week.
Republican Rep. Ed Royce, who is chairman of the House Foreign Relations Committee but did not sign the letter, said, "The president should be making the case to the American public, and his administration should come to Congress to explain their plans."
One key Democrat told CNN chief political analyst Gloria Borger that the Obama administration should not only put out evidence of the attack, but "additional evidence linking the regime to that use of chemical weapons."
"After all in Iraq there were claims that Saddam Hussein had stockpiles of chemical weapons. We went to war. It turned out not to be the case," said Rep. Chris Van Hollen of Maryland. "Now we know that (al-Assad) has stockpiles of chemical weapons. So the issue now is whether or not he used them. He of course has them. He has the delivery capability, and I believe the administration has additional evidence that will come forward."
But unlike some others, Van Hollen said he would support limited military action without prior congressional authorization if it were minor in scope and duration and did not put U.S. personnel at risk.
That could include the firing of cruise missiles from ships off the Syrian coast, considered by many watching the situation as the most likely avenue for the United States.
"If they want to take any action beyond that very narrow strike, they are going to need a congressional authorization going forward," he told CNN.
Sen. John McCain, an Arizona Republican and senior member of the Armed Services and Foreign Relations committees, appeared on CNN, arguing for a more forceful military action.
"We can reverse the situation on the battlefield by taking out his air assets, cratering his runways, and getting the weapons to the right people so that they can reverse the momentum," McCain said Tuesday on "The Situation Room with Wolf Blitzer."
"If it's simply just going and doing some cruise missile strikes, then I think again, it may be counterproductive, in fact it may give Bashar al-Assad a propaganda advantage by saying he was able to resist the United States attacks."
At least one Democratic senator sided with McCain. Sen. Chris Murphy, D-Connecticut, said in a statement, "There is little chance that targeted airstrikes would destroy Syria's chemical weapons stockpiles, making the strikes little more than a slap on the wrist. Moreover, those airstrikes would prompt a reaction from Assad as well as the countries that finance his murderous regime.
"Before engaging in a military strike against Assad's forces, the United States must understand that this action will likely draw us into a much wider and much longer-term conflict that could mean an even greater loss of life within Syria," he wrote, urging the U.S. continue to apply "concerted diplomatic, political, and economic pressure" on al-Assad.
The Armed Services Committee chairman, Democratic Sen. Carl Levin, said Tuesday he had been briefed and that the administration was "proceeding cautiously" and "consulting with our allies and other countries in the region. ...
"The president is considering a broad range of options that have been presented by our military leaders," Levin said in a statement.
Others on Capitol Hill said they had also discussed matters with the Obama administration, including Senate Minority Leader Mitch McConnell, House Armed Services Chairman Rep. Buck McKeon, House Speaker John Boehner and House Minority Leader Nancy Pelosi, CNN has learned.
In his conversation with White House officials on Monday, Boehner "made clear that before any action is taken there must be meaningful consultation with members of Congress, as well as clearly defined objectives and a broader strategy to achieve stability," his spokesman, Brendan Buck, said.
Carney said administration officials are "consulting with House and Senate leaders and leaderships of relevant committees."
– CNN coverage manager Steve Brusk, senior congressional producer Ted Barrett, Gregory Wallace and Tom Cohen contributed to this report.