The Saudi Arabia-led coalition fighting Yemeni rebels has said it will launch an investigation after more than 140 people were killed in air strikes on a funeral in the capital, Sanaa.
It would "immediately investigate this case" along with US experts.
Saudi Arabia earlier denied allegations from the rebel Houthi-run government that the coalition was responsible.
The attack targeted the funeral of the father of Houthi-appointed Interior Minister Galal al-Rawishan.
The Saudi-led coalition said in a statement: "The coalition will immediately investigate this case along with the Joint Incidents Assessment Team in Yemen and experts from the United States who participated in previous investigations."
It referred to "reports about the regrettable and painful bombing" in Sanaa, before adding: "The coalition confirms that its troops have clear instructions not to target populated areas and to avoid civilians."
The US said it had launched an "immediate review" of its already-reduced support for the coalition.
White House National Security Council spokesman Ned Price said US co-operation with Saudi Arabia was "not a blank cheque".
He said that while the US was focused on achieving an end to the conflict in Yemen, Washington was "prepared to adjust our support so as to better align with US principles, values and interests".
Houthi spokesman Mohammed Abdul-Salam said the attack was an act of "genocide".
UN humanitarian co-ordinator for Yemen, Jamie McGoldrick, condemned Saturday's strikes on the funeral gathering as a "horrific attack".
He said that aid workers who arrived at the scene had been "shocked and outraged".
The International Committee of the Red Cross (ICRC) said it had prepared 300 body bags.
The ICRC's Rima Kamal told the BBC "several air strikes" had hit the venue attended by hundreds of civilians and damage to the buildings was extensive.
The Saudi-led coalition is backing the internationally-recognised government of Yemen.
Thousands of civilians have been killed since the war began in 2014.