WASHINGTON (CNN) - As the Obama administration sells its plan for limited military strikes against Syria, an Arkansas Democrat says he "cannot support military action at this time."
Sen. Mark Pryor issued a statement Saturday saying President Obama and his national security team have not yet made an effective case for taking action against President Bashar al-Assad’s regime.
Pryor further criticized the administration for failing to lay out its big picture reasons for responding to Assad's alleged use of chemical weapons - namely, a "compelling national security interest" that demands the United States engage militarily.
"Based on the information presented to me and the evidence I have gathered, I do not believe these criteria have been met," Pryor said.
A more conservative Democrat, Pryor faces a tough re-election battle for the Senate against popular Republican Rep. Tom Cotton. Cotton said earlier this week he would support the authorization.
Pryor also stressed the need to "build a true coalition of allies" that would join the United States in punishing the Assad regime for violating international law.
The emphasis on international support for the Syria strikes comes follows a morning statement from European Union foreign ministers unequivocally condemning the August 21 chemical attacks as "a blatant violation of international law, a war crime and a crime against humanity."
Still, Pryor's decision to weigh in against the administration's plans could signal that momentum on the issue continues to move away from the White House. Pryor’s willingness to leave the door open to changing his vote also helps explain the urgent lobbying effort by the administration to "whip" Congress on Syria.
En route back from the G20 Summit in St. Petersburg, Russia, late Friday, Obama made several calls to congressional members on both sides of the aisle, according to a senior administration official.
While the official did not give the names or number of members Obama called, the mid-flight phone banking underscores the White House's continuous efforts to persuade members.
In addition to Obama, Vice President Joe Biden, Secretary of State John Kerry and White House chief of staff Denis McDonough continued to make calls to members, even after some attended a classified briefing Friday at the White House and U.N. Ambassador Samantha Power pitched the planned aerial assault in a speech to the Center for American Progress earlier in the day.
McDonough is scheduled to make appearances on all five major Sunday morning news shows only a week after Secretary of State John Kerry did the same.
The White House is tapping all its resources to sell its plan in the coming week, beginning with National Security Adviser Susan Rice's address to the New America Foundation on Monday.
The administration then plans to have the major players – Rice, Kerry, Secretary of Defense Chuck Hagel, Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey and Director of National Intelligence James Clapper - hold a closed intelligence briefing for the entire Congress on Monday at 5 p.m. ET.
The president himself is slated to address the nation Tuesday as Congress prepares to decide the fate of a resolution authorizing punitive strikes against Syria.
From a broad perspective, the Obama administration's momentum in persuading the nation to rally behind the president's plan seems to be slowing considerably.
Senate Majority Leader Harry Reid told reporters Friday he believes the resolution will get 60 votes in the Senate but added that rallying enough members to the president's side is "a work in progress."
The first of several key votes in the upper chamber - a procedural vote requiring at least 60 yeas for the Senate to formally take up the measure - is expected Wednesday.