Iran's supreme leader Ayatollah Ali Khamenei Thursday categorically ruled out talks with US President Donald Trump, despite an unprecedented Japanese mission aimed at defusing tensions between Washington and the Islamic Republic.

Iran “has no trust in America and will not in any way repeat the bitter experience of the previous negotiations with America,” Khamenei said in comments published by his official website.

They came after he met with Japan's Prime Minister Shinzo Abe making an unprecedented visit to Iran -- the first by a Japanese premier since the 1979 Islamic Revolution.

“We have no doubt in your good will and seriousness, but regarding what you said the US president told you, I don't consider Trump as a person worthy of exchanging messages with,” Khamenei told Abe during their meeting.

The visit coincided with a suspected attack on two oil tankers in the Sea of Oman, off the Iranian coast, with one of the ships owned by a Japanese company, which again sent tensions in the Gulf soaring.

Iran has been locked in a bitter standoff with the United States since Trump withdrew from a landmark 2015 nuclear deal in May last year.

Washington has since reimposed crippling unilateral sanctions — which have forced Tokyo to halt its once-substantial purchases of Iranian oil — and launched a military buildup in the Gulf.

“President Trump has said he does not wish to see an escalation of tensions,” Abe told reporters after his meeting.

“I shared candidly with Ayatollah Khamenei my own views about what intention the president has in mind,” Abe said, emphasising he had “exchanged views with President Trump several times”.

Trump indicated last week in France that he could consider talking to Tehran, saying: “I understand they want to talk and if they want to talk that's fine.”

Abe said he believed his meeting with Khamenei was “a significant step forward” for “securing peace and stability of this region.”

During a news conference with Abe on Wednesday, President Hassan Rouhani said he expected a “very positive change” in the Middle East and the world if the United States stopped what he called its “economic war” on Iran through sanctions.

Defusing tensions

Abe began his visit to Iran on Wednesday with the stated aim of defusing tensions between Tehran and Washington.

Japan stopped importing Iranian crude oil in May to comply with US sanctions against the Islamic republic.

The Asian powerhouse has an interest in keeping the Middle East stable in order to ensure the flow of hydrocarbons to fuel its economy.

Rouhani said Wednesday he saw “Japan's interest in continuing to buy oil from Iran and fixing financial issues” as a “guarantee” for the ongoing development of bilateral ties.

Spokesman for Japan's foreign ministry, Takeshi Osuga, later said that on the questions of Iranian oil sales to Japan, “our understanding is that this was the wish of the Iranian side.” But he added: “Oil purchase (from Iran) is the decision of private companies. I cannot predict their decision.”

The Japan PM met with Khamenei to deliver a message from Trump, the leader's website claimed, despite the Japanese delegation repeatedly denying that Abe was on a mediatory mission.