President Barack Obama's top diplomat and defense officials are set to testify before a Senate panel Tuesday on his request to authorize U.S. military action in Syria.
Secretary of State John Kerry, Defense Secretary Chuck Hagel and the Chairman of the Joint Chiefs of Staff General Martin Dempsey are all due to appear before the Senate Foreign Relations Committee.
Mr. Obama has said he wants congressional approval before launching a military strike on Syria for allegedly using chemical weapons against civilians.
White House officials are continuing to hold closed-door sessions briefing lawmakers in a bid to rally support for Mr. Obama's plan.
Senators John McCain and Lindsey Graham said they were encouraged after meeting with the president on Monday, but that they want to see some changes to the proposal. McCain expressed the need to weaken Syrian President Bashar al-Assad's capabilities while upgrading those of the rebels opposing him.