NEW YORK — The United States on Wednesday announced new sanctions to stop Iran from selling its oil, casting a cloud over last-minute European efforts to arrange a tension-reducing encounter between the adversaries' presidents.

French President Emmanuel Macron shuttled between his US and Iranian counterparts over two days at the United Nations, but acknowledged that time was running short.

On US President Donald Trump's last scheduled day at the annual UN summit of world leaders, his administration said it was imposing sanctions on Chinese companies that have purchased Iranian oil.

"We're telling China, and all nations — know that we will sanction every violation of sanctions of all activity," Secretary of State Mike Pompeo told a pressure group opposed to Iran's clerical regime on the sidelines of the United Nations.

China is believed to be the biggest foreign buyer of Iranian oil.

The Trump administration in May said that the United States would unilaterally force all countries to stop buying Iran's oil, its major export, sending tensions soaring.

The United States blamed Iran for an attack earlier this month on the oil infrastructure of Saudi Arabia.

France, Britain and Germany this week said they agreed with the US findings.

"Some have said that they've joined the United States; I think they have joined reality," Pompeo said of the Europeans.

But the European powers, while criticizing Iran, believe that diplomacy is the best way forward.

The Europeans want Trump to return to a nuclear accord negotiated by former President Barack Obama, under which Iran drastically reduced its nuclear program in return for unmet promises of sanctions relief.

"The conditions have been met for a rapid resumption of negotiations," Macron told reporters late Tuesday.

"It is now up to Iran and the United States to seize the opportunity," he said.

Trump, in a speech on Tuesday at the United Nations, warned that the United States would not ease economic pressure on Iran — a condition set by Iranian President Hassan Rohani for any meeting.

Despite his strong words, Trump is known for his fondness for made-for-television drama, as witnessed in his three meetings with North Korean strongman Kim Jong Un, and for following last-minute gut instincts.

Japanese Prime Minister Shinzo Abe and Pakistani Prime Minister Imran Khan both also met with the Iranian and US leaders. — AFP