Iran has ridiculed the resignation of the U.S. government's point man on Iran policy under President Donald Trump, accusing the White House of 'biting off more than they can chew.'

The mocking tweet, posted on August 7 by Foreign Ministry spokesman Abbas Musavi, came a day after the State Department announced that Brian Hook was departing.

Secretary of State Mike Pompeo said Elliott Abrams, another diplomat who has led the Trump administration's push to topple Venezuela's leadership, would temporarily take Hook's place.

No reason for Hook's departure was given.

In a post to Twitter, Musavi mocked the move, saying there was "no difference" between Hook and Abrams, and John Bolton, Trump's hawkish former national-security adviser.

"When U.S. policy concerns Iran, American officials have been biting off more than they can chew,' he wrote.

Hook's surprise departure came ahead of a planned UN Security Council vote next week to extend an arms embargo against Iran.

Hook became the U.S. special envoy in August 2018, not long after the Trump administration announced it would withdraw from the 2015 international nuclear accord that lifted crippling sanctions on Iran in exchange for Tehran agreeing to curb its nuclear ambitions.

Since then, the Trump administration has steadily ramped up its pressure and rhetoric against Tehran.

Despite severe economic problems, Iran's leadership has so far refused to budge or give in to U.S. pressure.

Abrams, who will be taking over from Hook, was a key figure in the 2003 Iraq War. He will take on the Iran portfolio as he continues his work seeking to topple Venezuelan President Nicolas Maduro, Pompeo said.

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