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.

Washington and Tehran have been conducting negotiations over the past month on a deal to curb Iran’s nuclear programme in return for the lifting of financial sanctions. A fourth round of talks is due to be held in Rome on Saturday.

On Wednesday Washington imposed sanctions on entities it accused of involvement in the illicit trade of Iranian oil and petrochemicals.

Separately, US Defense Secretary Pete Hegseth warned Iran that it would face consequences for supporting the Houthis, who control northern Yemen and have attacked ships in the Red Sea in what the group says is solidarity with the Palestinians.

Washington has been bombing the Houthis intensively since mid-March, hitting more than 1,000 targets. Tehran says the Houthis act independently.

Iran’s Foreign Ministry spokesperson Esmaeil Baghaei criticised “the contradictory approach of American decision-makers and their lack of goodwill and seriousness in advancing the path of diplomacy”, state media reported.

“The responsibility for the consequences and destructive effects of the contradictory behaviour and provocative statements of American officials regarding Iran will lie with the American side,” Baghaei said.

US President Donald Trump, who abandoned an earlier nuclear deal between world powers and Iran during his first term in 2018, has threatened to attack Iran unless it agrees a new deal. Both sides have so far described the previous rounds of talks, held weekly and mediated by Oman, as productive.