Iran on Tuesday welcomed Japan's offer to act as a mediator with the United States, with Foreign Ministry spokesman Abbas Mousavi calling a planned visit to Tehran by Japanese premier Shinzo Abe "a turning point."

Abe will meet Iranian President Hassan Rohani in Tehran in June, though an exact date has not yet been set, Mousavi was quoted as saying by state news agency IRNA.

The Japanese prime minister has good relations with both Iran and U.S. President Donald Trump, whose administration has increased the diplomatic pressure and reintroduced sanctions on Tehran. Trump has just left Japan after a four-day state visit.

>> Iran's supreme leader changes his tune on Rohani and Zarif | Explained

Abe said on Monday that Japan "wants to do all that it can" to resolve the Iran-U.S. conflict.

"We want to give diplomacy another try," Mousavi said, though he added that the fundamental basis for talks is respect for international agreements - which he said the United States had not shown with its unilateral withdrawal from the Iranian nuclear deal, struck in 2015. "That's why no talks are planned for the moment," Mousavi said.

Mousavi said that Iran wants the United States to pledge itself again to the agreement and to lift its sanctions on Iran. He also called on Europe to implement the agreement by the beginning of July, with particular weight placed on the lifting of all economic sanctions.

If the sanctions are not lifted, Iran would abolish the agreed limit on uranium enrichment, he said.

Trump said on Monday that he was willing to talk to Tehran. "The prime minister and Japan have a very good relationship with Iran," Trump said.

"I do believe that Iran would like to talk. If they would like to talk, we like to talk also," the president added.

Iran's foreign minister, however, was apprehensive about the offer, tweeting on Monday: "Actions- not words - will show whether or not that's Trump's intent."

Zarif in his tweet also blamed Trump's economic pressure on Iran for the regional tensions.