U.S. Secretary of State John Kerry said the United States is considering only an "unbelievably, small, limited" strike on Syria as punishment for allegedly using chemical weapons and he insisted military action will not end that country's civil war.

"We're not going to war," Mr. Kerry told reporters Monday after meeting with British Foreign Secretary William Hague in London. "We will be able to hold [Syrian President] Bashar al-Assad accountable without engaging troops on the ground or any other prolonged kind of effort, in a very limited, very targeted, very short-term effort that degrades his capacity to deliver chemical weapons without assuming responsibility for Syria's civil war. That is exactly what we are talking about doing; an unbelievably small, limited kind of effort."

Mr. Kerry acknowledged the difficult task he and President Barack Obama will have in getting Congress to approve a military strike on Syria. He recognized many people are opposed to the U.S. getting involved in another war because of the fallout from the invasion of in Iraq in 2003, which was based largely on incorrect intelligence about weapons of mass destruction. And he said Syria's civil war will not be settled through military means.

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"The end of the conflict requires a political solution," he said. "There is no military solution and we have no illusions about that."

Mr. Kerry also responded to comments President Assad made in an interview with CBS which is scheduled to be broadcast Monday. During the interview, President Assad denied he was behind the chemical weapons attack last month and rejected the evidence put forward by the Americans and other countries. He also threatened retaliation if there is a military strike.

"That kind of threat is nothing different from the threat we face every single day," Mr. Kerry said. "If we don't stand up to it, we'll face it more and they will think they can intimidate anybody. I don't believe that we should shy from this moment. The risk of not acting is greater than the risk of acting. And everybody needs to stop and think about that hard."

Mr. Kerry said he has every confidence in the material gathered by U.S. intelligence officials and added: "What does he offer? Words that are contradicted by facts and he doesn't have a very strong record with respect to this question of credibility… This is a man without credibility. And so I will happily stand anywhere in the world with the evidence we have against his words and his deception and his acts."

Mr. Kerry indicated that the U.S. has not made a direct tie between President Assad and the attack. However, he suggested that doesn't matter.

"The chemical weapons in Syria ... are controlled in very tight manner by the Assad regime," he said. "And it is Bashar al-Assad, Maher al-Assad, his brother [a military commander], and a general who are the three people who have control over the movement and use of chemical weapons. But under any circumstances, the Assad regime is the Assad regime and the regime issues orders and we have high level regime [members] that have been caught giving these instructions and engaging in these preparations."

Mr. Kerry also went on at length about the close ties between the U.S. and Britain. There have been concerns in Britain that relations have frayed somewhat since the House of Commons voted not to back Prime Minister David Cameron's decision to join the U.S. in a military strike on Syria. Mr. Kerry and others have instead praised France for agreeing to join the U.S.

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On Monday, Mr. Kerry sought to ease any concerns, speaking at length about the "special and essential" relationship between the countries.

"It was before a vote the other day in Parliament and it will be for long afterwards," he said. "Our bond is bigger than one vote, it's bigger than one moment in history."

He even invoked former British Prime Minister Margaret Thatcher. "As Margaret Thatcher put it pretty bluntly, as she did, the U.K. and the U.S. are real and true friends," he said.