The administration of U.S. President Donald Trump "does not deserve trust," and no effective negotiations will be held unless Washington eases "pressure" against Tehran by lifting economic sanctions, the Iranian ambassador to Japan told a news conference in Tokyo on Monday.

"We are facing pressure and, under such a situation, no effective talks or negotiations would be held," Morteza Rahmani Movahed told journalists at the Japan National Press Club through an interpreter who spoke in Japanese.

The ambassador said he feels "no sincerity" from the Trump administration, adding that Trump and some of his aides frequently make remarks that are not consistent with earlier statements on policy toward Iran.