The Obama administration is gaining ground in its bid to win congressional approval before launching a military strike on Syria. Arizona Republican Sen. John McCain met with Obama on Monday, along with fellow Republican Sen. Lindsey Graham of South Carolina. After the meeting, McCain told reporters he believes a vote against the strikes would have “catastrophic” consequences. The Senate Foreign Relations Committee will hold its first hearing on Obama’s proposal today. On Sunday, Secretary of State John Kerry said in television interviews that hair and blood samples from Syria have tested positive for the nerve agent sarin. His claims came a day after Obama made the announcement that he would seek congressional backing for military action following reports of a chemical weapons attack last month that the administration says killed more than 1,400 people outside the capital Damascus.

President Obama: “I’m confident in the case our government has made without waiting for U.N. inspectors. I’m comfortable going forward without the approval of a United Nations Security Council that, so far, has been completely paralyzed and unwilling to hold Assad accountable. Here’s my question for every member of Congress and every member of the global community: What message will we send if a dictator can gas hundreds of children to death in plain sight and pay no price?”

A report presented to the French Parliament Monday concluded the chemical attack was carried out by the Syrian government. The United Nations, meanwhile, says the number of civilians who have fled Syria has topped two million, with fear of Western air strikes helping to fuel the flow of Syrians into neighboring countries. Protests by antiwar groups against the proposed strike are continuing across the country and around the world.