WASHINGTON: After a clean sweep in five state primaries, Republican front-runner Donald Trump outlined an "America First" foreign policy during a speech here.

"It's time to shake the rust off America's foreign policy," he said during his speech at the Mayflower Hotel on Wednesday night.

"My foreign policy always puts the interest of the American people and American security above all else. Has to be first. Has to be. That will be the foundation of every single decision that I will make."

"'America first' will be the major and overriding theme of my administration," the Time magazine quoted the business mogul as saying.

Trump first used the phrase "America first"-which is associated with 1930s-era isolationism-in an interview with the New York Times in March.

In the speech, he criticised President Barack Obama's nuclear deal with Iran and his trip to Cuba, said he would fight the Islamic State (IS) terror group by being more "unpredictable" and also called for upgrading the US nuclear arsenal.

In his speech, Trump also offered an olive branch of sorts to Muslim allies of the US in rare remarks pointing to the ways in which tAmerica can have constructive relations with the Muslim world.

"We're going to be working very closely with our friends in the Muslim world, which are all at risk for violent attacks," he said.

Trump said he would also aim to hold talks with Russia to seek common ground, possibly over Islamist extremism.

"Some say the Russians can't be reasonable," he said. "I intend to find out."

China, he said, "respects strength, and by letting them take advantage of us economically like they are doing, we are losing all their respect". He said he would seek to "fix our relations with China" but did not suggest how.

The foreign policy speech is the second major speech in which he has sought to establish his bona fides for the Republican Establishment, analysts said.

In March, he gave a speech a speech to the American Israel Public Affairs Committee in which he mostly stuck to the script.

Trump won the Republican primaries in Connecticut, Maryland, Pennsylvania, Delaware and Rhode Island on Tuesday, putting him closer to clinching the nomination.

The wins decreased the odds for a contested convention this summer in Cleveland, a scenario his rivals had banked on to stop him from securing the Republican nomination.

"This to me was our biggest night," Trump said in his victory speech. "I consider myself the presumptive nominee."

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