UPDATE 1-Troop withdrawal in Yemen's Hodeidah could start Tuesday, Wednesday -U.N.

A redeployment of forces in Yemen's Hodeidah by the warring parties could start "possibly even today or tomorrow," United Nations Yemen envoy Martin Griffiths told the U.N. Security Council on Tuesday. The Iran-aligned Houthi movement and the Saudi-backed government agreed in talks in December to withdraw troops by Jan. 7 from Hodeidah under a truce aimed at averting a full-scale assault on the port and paving the way for negotiations to end the four-year war.

But the pact stalled over control of the Red Sea city, a lifeline for millions facing famine. After weeks of diplomacy, the United Nations said on Sunday that the parties had reached agreement on phase one of a troop redeployment. "The parties have agreed to redeploy from the ports of Saleef and Ras Isa in a first step, followed by a redeployment from Hodeidah port itself and critical parts of the city of Hodeidah associated with humanitarian facilities in step two," Griffiths told the 15-member Security Council on Tuesday.

"This will facilitate humanitarian access to the Red Sea Mills," he said. The World Food Programme grain stores at the Red Sea Mills are enough to feed 3.7 million people for a month and have been inaccessible for more than five months. The United Nations has warned the food is at risk of rotting. (Reporting by Michelle Nichols Editing by Chizu Nomiyama and David Gregorio)