A top Iranian military commander has threatened severe retaliation as tensions rise with the U.S. and Israel ahead of nuclear talks.

Iran accused the United States on Thursday of "contradictory behaviour and provocative statements" after Washington warned Tehran of consequences for backing Yemen's Houthis and imposed new oil-related sanctions on it in the midst of nuclear talks.

DUBAI, United Arab Emirates — Iran and the United States began a fourth round of negotiations Sunday over Tehran’s rapidly advancing nuclear program , officials said, just ahead of a visit by President Donald Trump to the Middle East this week.

Tehran official’s Beijing trip comes before third round of talks with the US and follows consultations with Russia.

The United States on Tuesday imposed sanctions on a network based in Iran and China that it accused of procuring ballistic missile propellant ingredients on behalf of Iran's Islamic Revolutionary Guard Corps as President Donald Trump's administration seeks to increase pressure on Tehran.

The United States issued new Iran-related sanctions on Wednesday, according to a notice posted to the U.S. Treasury Department's website. The sanctions target individuals and entities in China and Iran,

The United States on Wednesday unveiled fresh sanctions against six people and 12 firms -- including several Chinese nationals -- for their support of Iran's ballistic missile program.