London (AFP) - Donald Trump warned Monday he may end up having a bad relationship with British Prime Minister David Cameron, who branded the presumptive Republican presidential nominee's proposal to stop Muslim immigration to the US "stupid".

"It looks like we are not going to have a very good relationship," Trump told Britain's ITV television.

"Who knows, I hope to have a good relationship with him but he's not willing to address the problem either."

In December, Trump called for a "total and complete shutdown of Muslims entering the United States until our country's representatives can figure out what is going on", citing "great hatred towards Americans by large segments of the Muslim population".

Cameron branded the tycoon's stance as "divisive, stupid and wrong" and has refused to retract his comments, though he said on May 5 that anyone who comes through the US presidential primaries deserves "respect".

Cameron's spokesman told reporters Monday: "The PM has made his views on Donald Trump's comments very clear: he disagrees with them."

But he added: "He's been clear that he will work with whoever is president of the United States."

Trump insisted he was "not stupid... just the opposite", and denied he was divisive, calling himself "a unifier".

He told ITV his campaign trail policies were just "suggestions", but said there was a "tremendous" problem with Islamic extremism.

The tycoon rejected claims he was anti-Muslim.

"Absolutely not. I am anti-terror," he said.

Trump said he had "many Muslim friends", one of whom told him: "'Donald you have done us such a favour: you have brought out a problem that nobody wants to talk about'."

Trump also blasted the new London Mayor Sadiq Khan, the first Muslim elected to run a Western capital city.

Khan, who took office on May 9, has branded Trump "ignorant" on Islam and claimed the tycoon was making the world more dangerous by alienating mainstream Muslims.

Trump said he was offended by Khan's denouncement.

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"I think they were very rude statements and, frankly, tell him I will remember those statements. They are very nasty statements," Trump said.

"When he won I wished him well. Now, I don't care about him.

"Let's see how he does, let's see if he's a good mayor."

A spokesman for Khan on Monday again described Trump's views as "ignorant, divisive and dangerous".

"It's the politics of fear at its worst and will be rejected at the ballot box," the spokesman said.