The United States on Thursday imposed sanctions targeting Yemen's Huthi rebels as it voiced exasperation that the Iranian-banked insurgents have kept up a military campaign.

President Joe Biden's administration -- which has used sanctions more sparingly than Donald Trump's previous team -- also removed sanctions on several former Iranian officials, saying it was acknowledging changes in behavior.

The Treasury Department said it was imposing sanctions on several individuals including Said al-Jamal, a Huthi supporter who allegedly has run a smuggling network out of Iran to sell oil illicitly to benefit the insurgents.

Secretary of State Antony Blinken said it was hoping to exert pressure on the Huthi rebels to end their offensive launched in February to seize Marib, the last significant pocket of government-held territory in the north.

"It is time for the Huthis to accept a ceasefire and for all parties to resume political talks," Blinken said in a statement.

"The United States will continue to apply pressure to the Huthis, including through targeted sanctions, to advance those goals," he said.

The Biden administration, in one of its first steps, removed a last-minute designation by Trump of the Huthis as a terrorist movement.

Yemeni fighters loyal to the Iran-backed Huthi rebels perform a traditional dance during a rally to express solidarity with the Palestinians in the capital Sanaa on May 20, 2021
Yemeni fighters loyal to the Iran-backed Huthi rebels perform a traditional dance during a rally to express solidarity with the Palestinians in the capital Sanaa on May 20, 2021 AFP / MOHAMMED HUWAIS

The move came in response to fears from aid groups that they would need to pull out of Yemen as they are obliged to deal with the Huthis, who effectively are the government in vast areas including the capital Sanaa.

The Biden administration has ramped up diplomatic efforts on Yemen, which the United States considers the world's worst humanitarian crisis, and distanced itself from a devastating air campaign by neighboring Saudi Arabia.

Biden has also sought to re-enter a nuclear accord with Iran rejected by Trump. Indirect talks in Vienna have been held up by Iran's insistence on a complete removal of sanctions.

The Treasury Department said Thursday it was removing sanctions on three former Iranian officials including former National Iranian Oil Company chief Ahmad Qalebani.

"These delistings are a result of a verified change in behavior or status on the part of the sanctioned parties and demonstrate the US government's commitment to lifting sanctions in the event of a change in behavior or status for sanctioned persons," the Treasury Department said.

State Department spokesman Ned Price said the move was not linked to the talks on the nuclear deal in Vienna.

Critics of US sanctions policy have said that targeted individuals have little recourse to get off the blacklist, even if they address concerns.