Secretary of State John Kerry said Syrian President Bashar Assad could prevent a U.S.-led military strike by handing over all chemical weapons within the next week, as his tour to muster support for intervention arrived in London.
In a joint press conference with U.K. Foreign Secretary William Hague, Kerry said he appreciated that many people were opposed to military action in Syria, but stressed: "I think it's important for us to stand up as nations for civility and against actions that challenge notions of humanity and decency."
His comments come just two days ahead of a crucial vote in the Senate over a resolution authorizing a limited strike on Syria. President Barack Obama, who has repeatedly called for intervention, has accused Assad of launching a gas attack on Aug. 21 that killed over 1,400 people.
Kerry added that it was clear that the end of the conflict in Syria required a political solution, and said Assad could prevent a military strike by handing over all chemical weapons within the next week.
"Sure, he could turn over every single bit of his chemical weapons to the international community in the next week—turn it over, all of it without delay and allow the full and total accounting (of it), but he isn't about to do it and it can't be done," he said.
Instead, Kerry said that military action was needed to get Assad to enter into negotiations. "A resolution will not be found on the battlefield, but at that negotiating table—but we have to get to that negotiating table," he said.
(Read more: UK parliament votes against military action in Syria)
He continued: "We believe a strong international response is necessary to make sure atrocities like the one that Assad committed against hundreds of his own people will not happen again."
The U.K. parliament has already voted against military action in Syria, but Hague said the "objectives and efforts" of Britain remain closely aligned with that of the U.S.
"They (the U.S.) have the full diplomatic support of the United Kingdom," Hague said. Kerry added that the so-called "special relationship" between Britain and America remained as special as ever, despite the vote.
(Read more: Syria dominates G-20 as leaders express 'outrage')
On Sunday, Assad denied that his government had launched a chemical weapons attack in the country. Assad called on Washington to produce evidence that he was behind the attack, according to CBS, which reported the interview.