Biden also announced an end to 'relevant' US arms sales but gave no immediate details on what that would mean.
President Joe Biden announced on Thursday the United States was ending support for a grinding five-year Saudi-led military offensive in Yemen that has deepened suffering in the Arabian peninsula's poorest country, calling the move part of restoring a US emphasis on diplomacy, democracy and human rights.
"The war has created a humanitarian and strategic catastrophe," Biden told diplomats in his first visit to the State Department as president. "This war has to end."
The Yemen reversal is one of a series of changes Biden laid out on Thursday that he said would mark a course correction for US foreign policy. That is after President Donald Trump -- and some Republican and Democratic administrations before his -- often aided authoritarian leaders abroad in the name of stability.
The announcement on Yemen fulfils a campaign pledge. But it also shows Biden putting the spotlight on a major humanitarian crisis that the US has helped aggravate. The reversing of policy also comes as a rebuke to Saudi Arabia, a global oil giant and US strategic partner.
Saudi Arabia responded on Thursday, welcoming an assurance by Biden that the US would continue cooperation on the kingdom's defence. In a statement on the official Saudi press agency, the kingdom said it appreciated international diplomatic efforts, affirming "its firm position in support of a comprehensive political solution to the Yemeni crisis". The kingdom also stressed its humanitarian aid to Yemenis.
The ending of US support for the offensive will not affect any US operations against the Yemen-based al Qaida in the Arabian Peninsula, or AQAP, group, national security adviser Jake Sullivan said.
Biden also announced an end to "relevant" US arms sales but gave no immediate details on what that would mean. The administration already has said it was pausing some of the billions of dollars in arms deals with Saudi Arabia and the United Arab Emirates, Saudi Arabia's main partner in its Yemeni offensive.
While withdrawing support for Saudi offensive operations in Yemen, the Biden administration said it intends to help the kingdom boost its defences against any further attacks from Yemen's Houthis or outside adversaries. The assurance is seen as part of an effort to persuade Saudi Arabia and other combatants to end the conflict overall.
Saudi officials have offered a series of conciliatory gestures and remarks since Biden's election, seeking to soothe the 75-year-old relationship with the US. On Thursday, the State Department said the kingdom had conditionally released two dual Saudi-US citizens detained in a crackdown on civil society there, and reduced a sentence for a third, Dr Walid Fitaihi, convicted of "disobedience" to the government.
Yemen, the biblical kingdom of Sheba, has one of the world's oldest constantly occupied cities -- the more than 2,000-year-old Sanaa -- along with mud brick skyscrapers and hauntingly beautiful landscapes of steep, arid mountains. But decades of Yemeni misgovernment have worsened factional divisions and halted development, and years of conflict have now drawn in intervention by Saudi Arabia, the United Arab Emirates and Iran, which officials say has lent increasing support to the Houthis.
The Obama administration in 2015 gave its approval to Saudi Arabia leading a cross-border air campaign targeting the Houthi rebels, who had seized Sanaa and other territory and were sporadically launching missiles into Saudi Arabia.
US targeting assistance to Saudi Arabia's command-and-control was supposed to minimise civilian casualties in airstrikes. But Saudi-led strikes since then have killed numerous Yemeni civilians, including schoolboys on a bus and fishermen in their boats. Survivors display fragments showing the bombs to be American-made.
The stalled war has failed to dislodge the Houthis and is helping deepen hunger and poverty. International rights experts say both the Gulf countries and Houthis have committed severe rights abuses.
Yemeni activist Tawakkol Karman, a co-winner of the 2011 Nobel Peace Prize for her role in Yemen's unsuccessful Arab Spring popular uprising, urged Biden to stay involved in Yemen peace efforts.
"Deeper US engagement -- and a refusal to side with dictators who have chosen bloodshed over democratic change -- is vital so that the Yemeni people can return to the project of democracy" that warring parties inside and outside of Yemen interrupted, Karman said in a statement.
UN spokesman Stephane Dujarric said the US action will give more space and more hope "not only to the talks but, more importantly, more hope to the people of Yemen".
Biden called on Thursday for a ceasefire, an opening of humanitarian channels to allow more delivery of aid and a return to long-stalled peace talks.
The weeks-old Biden administration has made clear that shifting its stance toward the Yemen war, and toward Saudi Arabia over the Yemen offensive and other rights abuses, was a priority. Other measures have included a review of the Trump administration's categorisation of the Houthis as a terror group. Critics say the designation hinders delivery of humanitarian aid to Yemenis.
Biden also announced the choice of Timothy Lenderking as special envoy to Yemen.
Lenderking has been a deputy assistant secretary of state in the department's Middle East section. A career foreign service member, he has served in Saudi Arabia, Kuwait and other countries in the Middle East and elsewhere.