"Delaying the release of Iran's assets in Japanese banks is unjustifiable," Raisi told visiting Japanese Foreign Minister Toshimitsu Motegi, the government website reported.

Japan and to a larger extent South Korea are both major exporters of technology, and hold billions of dollars in Iranian assets.

These funds have been frozen since the former US president Donald Trump unilaterally withdrew Washington from a landmark nuclear deal and reimposed sanctions on Tehran in 2018.

Washington said in mid-July that it was allowing Iran to use the frozen funds to settle debts in South Korea and Japan, but insisted that it did not allow any to be transferred to Tehran itself.

Talks between Iran and world powers aimed at reviving the 2015 accord have stalled since late June. The United States has been involved indirectly in the talks.

Motegi arrived in Tehran early Sunday after visiting Turkey and Iraq during a regional tour, and he will also go to Qatar.

At a press briefing after meeting Raisi, Motegi told Japanese reporters that during his visits he had discussed the situation in Afghanistan following the capture of Kabul by the Taliban.

He said he agreed with Iran, Turkey and Iraq on the need to cooperate to avoid Afghanistan becoming a "further destabilising factor".