Yemen's Houthi rebels have said they will no longer allow child soldiers to join their ranks and will release those who have joined, according to the UN.
The Iran-backed rebels will identify and release children in their ranks within the next six months, UN spokesman Stephane Dujarric said.
Thousands of children have fought in the country's civil war, but the Houthis have agreed to what the UN described as an action plan in a ceremony in Yemen's capital, Sanaa, on Tuesday.
UN children’s agency Unicef aims to end child recruitment in armed conflicts, the killing and maiming of children in warfare and attacks on schools and hospitals.
One of the Houthis top diplomats, Abdul Eluh Hajar, signed the agreement and said the plan is to protect children.
Virginia Gamba, the UN's top official for children in war zones, called the Houthis' move “a positive and encouraging step”, but said “the most difficult part of the journey starts now”.
“The action plan must be fully implemented and lead to tangible actions for the improvement of the protection of children in Yemen,” Ms Gamba, who signed as a witness to the Houthis’ commitment, said.
The UN says nearly 3,500 children have been verified as recruited in Yemen's civil war.
However, a senior Houthi official told AP in 2018 that the group had inducted 18,000 child soldiers into its army. Former child soldiers told the agency that boys as young as 10 were recruited.
At the time, a Houthi military spokesman denied the systematic recruiting of people under 18 and said there were orders to reject children who tried to join up.
More than 10,200 children have been killed or maimed in the war, the UN says. It is unclear how many may have been combatants.
Yemen's internationally recognised government, backed by a Saudi-led coalition, has been in conflict for seven years against the Houthis.