The UN Security Council has agreed to deploy a team to the Yemeni port of Hudaydah to oversee a ceasefire there.
The truce began on Tuesday after being agreed at UN-sponsored talks last week between delegations from the Yemeni government and Houthi rebels.
Britain drafted the UN resolution, the first on Yemen for three years.
It was approved after negotiations during which the US pushed for the resolution to be stripped of language calling for war crimes accountability.
The UN team will be deployed for an initial 30 days to monitor and help implement the ceasefire deal.