John Kerry has reiterated his case for armed intervention in Syria, arguing that inaction would make the situation worse.
The US secretary of state spoke before the US Senate's Armed Services Committee on Tuesday, a day after the chamber decided to delay a vote on use of force, originally scheduled for Wednesday.
He told the committee that Syrian President Bashar al-Assad had responded to calls for diplomacy with violence, and that it was the Syrian regime, not the US government, that had chosen the current situation.
Kerry also argued that not resolving to strike would result in "irreparable damage" to the prohibition on chemical weapons that has "protected American troops for centuries".
Shortly following this staunch argument, Russian president Vladimir Putin said the proposal for Syria to place its chemical weapons under international control "can work only if we hear that the American side and all those who support the United States in this sense reject the use of force."
During his address to the Senate, Kerry also said that lack of military intervention would "send a message to Iran of American weakness."
But he repeated President Barack Obama's desire for a diplomatic resolution. "President Obama's first priority throughout this process has been and is diplomacy," he said.
Kerry's remarks come the day after Obama said he would consider a Russian diplomatic offer for Syria to give up its chemical weapons and that military strikes would "absolutely" be put on hold if that were to happen.
Obama made the statements late on Monday as the US Senate decided to delay its vote on military action - capping a day of shifting positions from within the administration and on Capitol Hill.
Since Russia's proposal that Syria hand over its chemical weapons to international control in order to avert airstrikes, the US has been seen as trying to walk a line between not ruling out a diplomatic solution to the conflict, while also leaving military intervention on the table.
US administration has said it would take a "hard look" at the proposal, but indicated that Syria would have to follow through with its acceptance of the proposal with concrete action.
|US Congressman John Garamendi speaks to Al Jazeera
The current debate began with Secretery of State John Kerry saying, in response to a reporter's question, that there would be no need for military action if Syrian President Bashar al-Assad handed over his chemical weapons - an answer that was then presented by Russian foreign minister, Sergey Lavrov, as a workable plan.
The US administration at first stated that Kerry's response was only rhetorical, but within hours the president said in interviews with six US networks that a diplomatic solution should be sought.
Obama said on CNN that the Russian plan was "a potentially positive development", while on NBC he said it could be a "significant breakthrough".
He was also adamant that the offer would not have surfaced if "a credible threat of a military strike from the United States" had not been made.
He told PBS: "I have instructed John Kerry to talk directly to the Russians and run this to ground and if we can exhaust these diplomatic efforts and come up with a formula that gives the international community a verifiable enforceable mechanism to deal with these chemical weapons in Syria, then I'm all for it."
Obama also conceded that he may lose his campaign in Congress for authorisation.
"I wouldn't say I'm confident," he said.
Iran's Foreign Ministry on Tuesday said it supported the idea while Ban Ki-moon, the UN secretary-general, said he too welcomed it.