US President Donald Trump on Tuesday denounced Iran's “blood lust” and called on other nations to join the United States to pressure Iran after attacks on Saudi oil facilities but said there is a path to peace.

“We want partners, not adversaries,” Trump said in an address to the United Nations General Assembly annual gathering of world leaders.

In his third annual appearance at the United Nations, Trump offered a more subdued tone compared to the bombast of his previous speeches to the UN in 2017 and 2018, looking to convey a more reassuring presence as he asks Americans for a second term next year despite a fresh push for his impeachment among some Democrats.

While offering his habitual defence of national sovereignty, Trump tempered his language toward Iran, stressing the US desire for peaceful relations with all and calling for collective, rather than unilateral, action. “America's knows that while anyone can make war, only the most courageous can choose peace,” he said.

The September 14 attacks in Saudi Arabia have rattled the Middle East and raised concerns about a broader war. Trump has shown restraint in the crisis, holding back from military retaliation despite pressure from conservative hawks, at least for now.

But he promised to keep trying to squeeze Iran's economy with sanctions until Tehran agrees to give up what Washington says is a pursuit of nuclear weapons. Iran has said its nuclear programme has always been for peaceful purposes only.

“All nations have a duty to act. No responsible government should subsidise Iran's blood lust. As long as Iran's menacing behaviour continues sanctions will not be lifted, they will be tightened,” Trump said.

Trump had a stern message for China and its president, Xi Jinping, with whom he is locked in a trade war that is damaging both their economies. He said the world is watching how Beijing handles mass demonstrations in Hong Kong that have raised concerns about a potential Chinese crackdown.

“How China chooses to handle the situation will say a great deal about its role in the word in the future. We are all counting on President Xi as a great leader,” he said.

Trump has sought to pressure China to agree to reduce trade barriers through a policy of increasing tariffs on Chinese products.

“Hopefully we can reach an agreement that will be beneficial to both countries. But as I have made clear I will not accept a bad deal for the American people,” Trump said.

Trump was tough on Iran and its leadership, with Iranian President Hassan Rouhani in New York for UN activities amid speculation about whether they might meet to discuss their differences.

Rouhani was at his New York hotel, not in the UN chamber, during Trump's speech.

Take a look: Rouhani heads to UN in quest to win Iran support against US

In remarks to media on Tuesday Rouhani said he was open to discuss small changes, additions or amendments to a 2015 nuclear deal between Iran and six major powers if the United States lifted sanctions imposed on the Islamic republic.

French President Emmanuel Macron, trying to create conditions for talks between the United States and Iran, said he hoped there could be progress on Iran on Tuesday after he held talks with Rouhani on Monday.

“We have to get back around the table to have a frank and demanding discussion on the nuclear activity, Iran's regional activities, the ballistic missile program, but also to have a larger approach on what sanctions are,” Macron told reporters, without elaborating. “I hope we will be able to make progress in the coming hours.”

Tehran has been widely blamed for the attacks in Saudi Arabia but it denies involvement. Over the past week, Trump has tightened economic sanctions on Iran and ordered more US troops to Saudi Arabia and the United Arab Emirates in a show of support for those US allies in the tense region.

“After four decades of failure it is time for Iran's leaders to step forward and to stop threatening other countries and focus on building up their own country,” Trump said.

“America is ready to embrace friendship to all who genuinely seek peace and respect,” he said.