Trump says Xi agrees Iran must open strait, China says war should not have started

US President Donald Trump said Chinese President Xi Jinping had agreed Tehran must reopen the Strait of Hormuz, though China gave no indication it would weigh in.

Flying back from Beijing on Friday after two days of talks with Xi, Trump said he was considering whether to lift US sanctions on Chinese oil companies buying Iranian oil. China is the biggest buyer of Iranian oil.

"I'm not asking for any favors because when you ask for favors, you have to do favors in return," Trump said when asked by a reporter on Air Force One whether Xi had made a firm commitment to put pressure on the Iranians to reopen the vital strait.

Xi did not comment on his discussions with Trump about Iran, although China's foreign ministry criticised the war, calling it a conflict, "which should never have happened, has no reason to continue".