President Donald Trump told Chinese ​leader Xi Jinping it would be “unacceptable” for China to help Iran during the US’s military campaign against the country, the US ambassador to China said.

The warning came amid reports that China had supplied Iran with missile launchers and that Iran had evaded sanctions on its oil sales with Chinese ​help.

China has denied the allegations.

David Perdue told CNBC, “We made ⁠it very clear to them weeks ​ago that, ‌you know, any help ‌that they would give Iran, ‌whether it be direct or indirect, whether it be intelligence or parts or military equipment, was totally unacceptable. President Trump made that very clear again ‌yesterday.”

Perdue told Fox News the US had received assurances from China that it would stop assisting Iran.

“We’ve seen movement … on that already. That’s what the commitment is. They assured us yesterday they’re not doing that.”

Trump and Xi have wrapped up their three-day summit with a visit to the National Archives and tea at the White House, in an encounter that showcased personal diplomacy rather than big breakthroughs in economic relations.

The US and Chinese presidents and their wives having tea in the Red Room. Photo: AP

Trump said the summit had produced great strides and that “I think our farmers are going to be happy” but did not provide details.

“America is very happy about this visit and I’m sure China is very happy also,” he said.

Xi said the US-China relationship had developed ‌into a constructive one of “strategic stability on the basis of respect, fairness and reciprocity”.

Xi also said he and Trump would have two more opportunities to meet this year, the APEC summit in China and a G20 summit in Miami.

“I do welcome you, Mr President and the First Lady to visit China,” he said.

Trump later said he had accepted Xi’s invitation.

“We will be meeting again in November, in China, and then at the G20 in December, in Miami, Florida. Much has been, and will be, accomplished,” Trump wrote on his Truth Social platform.

The lavish state summit, with flyovers, tours and a glittering state dinner, has been heavy on symbolism but light on substance.

Still, Trump highlighted progress under a bilateral trade mechanism, citing what he described as increased market access for US farmers and ranchers, while both leaders identified artificial intelligence as an area for co-operation.

Details of the limited agreements the two sides struck regarding their tense trade relationship would be released on Monday, US Trade ‌Representative Jamieson Greer told CNBC ‌on Friday.

“We’re in a managed trade situation … ⁠We’ve had progress, and we will release on Monday, I think, a lot more details about what we’ve accomplished over the past few weeks in ​negotiating with the Chinese,” he said.

The US has agreed with China on exempting some key goods from arguments over trade, Greer said, including exports to China of agricultural products and medical devices and imports of consumer and non-sensitive goods.

The summit concluded at the National Archives, where Trump and Xi appeared to review the US declaration of independence and the constitution and the bill of rights.

They would also see “artefacts testifying to the long and cherished relationship” between China and the US and their “cultural exchanges,” Trump said in remarks welcoming Xi on Thursday.

“Just as our ancestors reached across the ocean centuries ago to trade, to learn and to build a better world, our two countries do really the same thing, and we’re very proud of it and ⁠the relationship,” Trump said.

China has not commented on the visit to the archives but analysts say Xi may be keen to ‌see records relating to the ​US switch of recognition to communist China from Taiwan in 1979.

-with AAP