King Charles ribbed Donald Trump that Americans would be speaking French if it were not for the British, even as the US President said that Britain's monarch did not want Iran to have a nuclear weapon, introducing the fraught subject of the Middle East conflict into comments at a White House state dinner for the visiting royal.

“You recently commented, Mr. President, that if it were not for the United States, European countries would be speaking German. Dare I say that if it wasn't for us, you'd be speaking French,” Charles said in his speech.

He also seemed to take a dig at Trump’s redevelopment of the White House’s East Wing, and said: “I am sorry to say that we British, of course, made our own attempt at real estate redevelopment of the White House in 1814.”

On August 24, 1814, British forces captured Washington DC after defeating American troops at Bladensburg, Maryland. They burned major public buildings, including the White House and the Capitol, as retaliation for the American attack on York.

Charles also called the White House state dinner “a very considerable improvement on the Boston Tea Party,”

The event was held on the second day of Charles’s four-day visit to the US at a tense time in ties, after Trump has repeatedly criticised British Prime Minister Keir Starmer for what Trump calls lack of help in prosecuting the Iran war.

"We're doing a little Middle East work right now and we're doing very well," Trump said at the dinner.

"We have militarily defeated that particular opponent, and we're never going to let that opponent ever – Charles agrees with me even more than I do - we're never going to let that opponent have a nuclear weapon."

He also said: "I want to congratulate Charles on having made a fantastic speech today at Congress. He got the Democrats to stand; I've never been able to do that."

In his comments following Trump, Charles did not speak about Iran or the war. The king is not a spokesman for the British government.

Asked about the state dinner comments, the British embassy in Washington referred Reuters to Buckingham Palace, which did not immediately respond to a request for comment.

In a speech to Congress earlier, Charles made no direct mention of the Iran war, but referred to Trump's criticism of Nato, highlighted the importance of continued US\ help for Ukraine in its war with Russia, and the dangers of isolationism.

Both Britain and the US have maintained over the years that Tehran should not develop nuclear weapons.

Tehran, which does not have nuclear weapons, denies seeking them but says it has the right to develop nuclear technology for peaceful purposes, including enrichment, as a party to the Nuclear Non-Proliferation Treaty.