Yemen's Houthi group intends to withdraw forces from three key ports in Yemen over four days, starting on Saturday, said a senior United Nations official in charge of monitoring the move.

The Houthi movement and the Saudi-backed Yemen government initially agreed in December to withdraw troops by Jan. 7 from Hodeidah - a lifeline for millions facing famine - 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.

Lt. Gen. Michael Lollesgaard, who heads a UN mission to monitor the deal, said the Houthis intended to start withdrawing on Saturday from the ports of Hodeidah, Salif and Ras-Issa.