Fred Thompson, the actor and former US senator, has given his strongest indication yet that he is preparing to launch a presidential campaign in the next few weeks.

In an exclusive interview, his first with a non-US news organization, the former lawyer and star of "Law and Order", the US detective show, told The Times that his presidential bid would be based on his belief that Americans wanted change and that he was uniquely placed to provide it.

“I think they perceive the reality and the reality is that perhaps this is the occasion where the man meets the times.”

He said he had the experience for a tough presidential campaign in an already crowded field for the Republican nomination in next year’s presidential election. “As we say where I grew up this ain’t my first rodeo. I’ve seen it up close and personal. I’ve had good friends run for president. I've campaigned for them. I’ve known a few presidents. I understand what the job is about and I wouldn’t run for it if I wasn’t willing to pay the price”.

Mr Thompson expressed pleasure at recent poll numbers that have propelled him to the front of the Republican presidential field, even before he has formally declared, though he acknowledge he was entering with high expectations.

“You start out with these kinds of poll numbers and you have a level of expectation. But frankly I’d rather have that problem than the problem that some of the others have.”

Mr Thompson is running roughly neck-and-neck with Rudolph Giuliani in early Republican polls. There is a high level of dissatisfaction with all the current leading candidates, especially among conservatives. Mr Giuliani, John McCain, the former Arizona senator, and Mitt Romney, the former Massachusetts governor, are all seen as not reliably conservative by many of the party’s base. Mr Thompson, by contrast, is expected to run as a more conventionally conservative candidate.

But he is also seeking to distance himself from the unpopular incumbent president, George Bush. In the interview Mr Thompson was strongly critical of the conduct of the Iraq war, and said America would proceed with a greater “dose of realism” in the future.

But he insisted the original decision to go to war was “just” and said the US was right to try to promote democracy around the world.

The former senator was visiting London at the invitation of Policy Exchange, the conservative-leaning think-tank. He met David Cameron, the Conservative leader and Lady Thatcher, the former prime minister.

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