Britain and the US will never again invade sovereign foreign countries “in an attempt to make the world in their own image,” Theresa May told Republican policymakers in Philadelphia.

The Prime Minister vowed never to repeat the “failed policies of the past” in reference to Western military intervention in Iraq and Afghanistan, breaking from the “liberal intervention” principle established by Tony Blair.

Referencing the “special relationship” between the UK and US, Ms May also stressed the importance of cooperation between the two countries to meet their “obligations of leadership” and “stand up for our interests".

“It is in our interests – those of Britain and America together – to stand strong together to defend our values, our interests and the very ideas in which we believe,” she said.

"This cannot mean a return to the failed policies of the past. The days of Britain and America intervening in sovereign countries in an attempt to remake the world in our own image are over.”

However she called for “strong, smart and hard-headed” actions to stand up for Western principles, adding: “Nor can we afford to stand idly by when the threat is real and when it is in our own interests to intervene.”

She also pledged support to Mr Trump in the continued fight against the “new enemies of the west and our values”.

Ms May said it was a “priority” to push back on “Iran’s aggressive efforts” to increase its "arc of influence from Tehran through to the Mediterranean". However, she defended the nuclear deal brokered by Barack Obama despite threats from Mr Trump that he would rip up the agreement, saying it had been successful in neutralising a potential threat.

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She also delivered a stark warning to Mr Trump on Russia, saying: “With President Putin, my advice is to engage but beware.”

The speech, delivered on the Prime Minister’s first leg of her US visit, will be followed by a face-to-face meeting with Mr Trump on Friday in Washington, part of a determined push by the Prime Minister to seek US commitment to a trade deal when Britain leaves the EU.

The President’s allies have told the Prime Minister’s team that they could “do a trade deal in a week” – provided it is on favourable terms.

But Mr Trump has taken a highly-protectionist stance and Britain risks inflaming tensions with the EU if it breaks the rules on negotiating new agreements while still a member.

Ms May will be the first foreign leader to meet the President since his inauguration last week.