The UN envoy for Yemen arrived in the capital Sanaa on Saturday for talks to shore up a ceasefire in the country's lifeline port city of Hodeidah, an AFP photographer said.
Martin Griffiths is scheduled to hold talks in Sanaa with Houthi rebel leaders and will later travel to the Saudi capital Riyadh to meet Yemeni government officials.
He will also meet in the rebel-held capital with retired Dutch general Patrick Cammaert, who has been appointed by the UN to head the truce monitoring team.
Griffiths' visit comes as the ceasefire in Hodeidah was generally holding, although there have been intermittent clashes with both sides blaming each other.
Yemen's government has written to the UN Security Council to accuse rebels of failing to comply with the ceasefire, while the rebels have accused the Saudi-led coalition of carrying out low-altitude flights over the city.
The United Nations is hoping to bring the warring sides together later this month, possibly in Kuwait, to follow up on the progress made at December's talks in Stockholm, diplomats have said.
The UN Security Council is expected to hear a report from Griffiths next week, but no date has been set for that meeting.
The war between the Houthis and troops loyal to the internationally-recognised government escalated in March 2015, when President Abedrabbo Mansour Hadi fled into Saudi exile and the Saudi-led coalition intervened.
The conflict has unleashed the world's worst humanitarian crisis according to the UN, which says 14 million Yemenis are on the brink of famine.
Members of the Yemeni pro-government forces gather at the eastern entrance of the port city of Hodeidah on December 30, 2018