A Senate panel has voted to give US President Barack Obama the authority to use military force against Syria in response to a deadly chemical weapons attack, adding momentum to the White House's push to win congressional backing for a strike.
The vote in the Senate Foreign Relations Committee was the first in a series as the president's request makes its way through congressional panels before coming before the two chambers of Congress for a final vote.
The full Senate is expected to vote on the measure next week.
Mr Obama's top advisers took the argument for action to the Republican-controlled House of Representatives today, where the support seen in the Senate will be harder to find.
The resolution would permit Mr Obama to order a limited military mission against Syria, as long as it does not exceed 90 days and involves no American troops on the ground for combat operations.
The Senate committee vote was 10-7. It marked the first time politicians have voted to authorise military action since the October 2002 votes giving president George W Bush the authority to invade Iraq.
Mr Obama, who was visiting Sweden before he attends a G20 economic summit with Russia later this week, said the international community's credibility is at stake in the debate over a military response to the use of chemical weapons in Syria.
The Obama administration said a sarin gas attack by Syrian President Bashar Assad's forces outside Damascus last month killed more than 1,400 people. Assad's government has denied being behind the attack.
Asked about his past comments drawing a "red line" against the use of chemical weapons, Mr Obama said that line had already been drawn by a chemical weapons treaty ratified by countries around the world.
"That wasn't something I made up," he said.
The Senate committee's vote had been delayed after Republican Senator John McCain, an outspoken advocate of intervention against the Assad regime, said he does not support the resolution. He said he wants more than cruise missile strikes and other limited action, seeking a stronger response aimed at "reversing the momentum on the battlefield" and hastening Assad's departure.
The Obama administration also needs to persuade a Republican-dominated House of Representatives that has opposed almost everything on Mr Obama's agenda since the party seized the majority more than three years ago.
The top Republican in Congress, House Speaker John Boehner, has signalled key support, saying the US has "enemies around the world that need to understand that we're not going to tolerate this type of behaviour."
On Saturday, Mr Obama unexpectedly stepped back from ordering a military strike under his own authority and announced that he would seek congressional approval.
Reporters asked him today whether he would take action against Syria if he fails to get that approval. As commander in chief, "I always preserve the right and the responsibility to act on behalf of America's national security", he said.
The administration said 1,429 people died from the gas attack on August 21. The British-based Syrian Observatory for Human Rights, which collects information from a network of anti-government activists in Syria, said its toll has reached 502. Assad's government blames the attack on the rebels.
A United Nations inspection team said today that it is speeding up its analysis of tissue and soil samples it collected in Syria last week and hopes to have it done in two or three weeks.
Also today, Secretary of State John Kerry, Defence Secretary Chuck Hagel and the chairman of the Joint Chiefs of Staff, General Martin Dempsey, were trying to make their case in a public hearing before the House Foreign Affairs Committee.
Mr Kerry said that when chemical weapons were used in Syria last spring, Mr Obama did not have a "compelling" enough case to push for a US military response.
Mr Kerry also said US intelligence can prove Assad has used chemical weapons at least 11 times, and said North Korea and Iran are watching the US closely.
"The world is wondering whether the United States of America is going to consent with silence," he said.
Anti-war demonstrators seated behind him silently raised their red-coloured hands.
But even supporters of military action urged Mr Obama to do more to sell his plans to an American public that is highly sceptical after a decade of war in Iraq and Afghanistan.
The president is expected to find little support for action on his overseas trip. Among major allies, only France has offered publicly to join the US in a strike. UN Secretary-General Ban Ki-moon has warned that any "punitive" strike on Syria would be illegal without a sound case for self-defence or the approval of the Security Council, where Syria ally Russia has used its veto power to block action against Assad's regime.
Russian President Vladimir Putin has warned the West against taking one-sided action in Syria but said Russia "doesn't exclude" supporting a UN resolution on punitive military strikes if it is proved that Syria used poison gas on its own people.
In an interview with the Associated Press yesterday, Mr Putin expressed hope that he and Mr Obama would have serious discussions about Syria and other issues at the G20 summit in St. Petersburg this week.
Mr Obama said today that he is "always hopeful" that Mr Putin will change his position on taking action in Syria.