The United States on Tuesday called on its arch-enemy Iran to help end the conflict in Yemen by supporting the peace process, a year after a truce that significantly reduced violence.

Last month, Iran, which backs the Houthi rebels who control much of the country, announced a reconciliation deal with Saudi Arabia, which is leading a military campaign in support of the Yemeni government.

"If the Iranians really want to show that they are bringing about a positive shift in the conflict, then there will be no more arms smuggling to the Houthis in violation of UN Security Council resolutions," said Timothy Lenderking, the US special envoy to Yemen.

"We'd also like to see the Iranians show their support for the political process that we hope will come," Lenderking said at the Middle East Institute in Washington.

Lenderking noted positively that Iran welcomed the cease-fire a year ago. The truce ended in October, in large part because the Houthis demanded the payment of salaries to employees in areas under their control, but there has been no resumption of large-scale fighting.

"We urge the parties to seize this opportunity, knowing that an agreement will require concessions from all," Lenderking said.

Nearly a decade of war in Yemen has killed hundreds of thousands, directly and indirectly, and most of the population has depended on aid to survive.

President Joe Biden pledged, as he took office, to give greater priority to ending the bloody conflict in Yemen, after the strong support that his predecessor, Donald Trump, provided to the Saudis.

The Saudi-Iranian deal was announced by China, which has played an unusually prominent role in a region where the United States is the primary power.

The United States has severed diplomatic relations with Iran since the 1979 Islamic Revolution overthrew the pro-Western shah.