Lawmakers demanded changes Wednesday to the authorization for the use of US military force against Syria before a crucial vote on President Barack Obama's call for punitive strikes.
The Senate Foreign Relations Committee held a three-hour, classified session to try to thrash out an agreement after Republican veteran Senator John McCain appeared to balk at the plan because it did not go far enough.
"Without the provision on reversing the momentum on the battlefield, then conditions are not created for the departure of (Syrian president) Bashar al-Assad," McCain told reporters after emerging from the briefing.
"We need to have that provision," McCain insisted. "There is no policy without that, and there is no strategy without that."
Secretary of State John Kerry briefed the committee behind closed doors before rushing to provide testimony at a panel of the House of Representatives, where lawmakers and analysts foresee a tough fight over Obama's military strike plan.
"We need to send to Syria -- and to the world, to dictators and terrorists, to allies and civilians alike -- the unmistakable message that when we say never again, we actually don't mean sometimes, we don't mean somewhere, we mean never again," Kerry told the House Foreign Affairs Committee.
"As we debate, the world is watching and the world is wondering, not whether Assad's regime actually did this," Kerry added.
"The world is wondering whether the United States of America is going to consent through silence to stand aside while this kind of brutality is allowed to happen without consequence."
Democrat and Republican leaders in the Senate Foreign Relations Committee had announced a bipartisan resolution and scheduled a markup and vote for mid-day Wednesday, but it got bumped back a few hours amid what was clearly dissent about the path forward.
Asked whether a vote on the resolution -- which will be subject to votes on several amendments -- was likely Wednesday, committee chairman Senator Robert Menendez said, "I believe we'll get there."
Number two Senate Democrat Dick Durbin, who has not said whether he supports Obama's plan, said he is introducing an amendment that calls for being "more specific in terms of the authority of the president in Syria."
Democratic Senator Chris Coons said he filed an amendment that addresses the humanitarian impact on US regional allies of two million refugees from Syria.
Republican Senator Ron Johnson has voiced skepticism about the wisdom and cost of the intervention, and on Wednesday he said the Senate and administration were moving too quickly.
"I think a vote today is ridiculous," he told AFP after the closed-door briefing.
"We're rushing this process, and there's no need to."