The United Nations special envoy to Yemen urged warring parties Monday to quickly implement a troop withdrawal from the port of Hodeidah, acknowledging that proposed timelines had slipped while the country stood on the brink of famine.

The U.N. Envoy Martin Griffiths hosted hard-won peace talks between the Saudi-backed Yemeni government and rival Iran-aligned Houthi rebels in Sweden last month. Griffiths, who arrived yesterday in Sanaa on his third trip to Yemen this month, said there had been "changes in timelines" for both deals.

"That momentum is still there, even if we have seen the timelines for implementation extended, both in Hodeida and with regard to the prisoner exchange agreement," he told Saudi-owned newspaper Asharq Al-Awsat. "Yet such changes in timelines are expected, in light of the facts that the timelines were rather ambitious and we are dealing with a complex situation on the ground." Agreements reached in December between the Iranian-aligned Houthi movement and the Saudi-backed government of Abed Rabbo Mansour Hadi were the first significant breakthrough in nearly five years of conflict which has killed tens of thousands of people. But little progress has been made on the trust-building measures, risking the unravelling of peace efforts.

Implementation of the deal, the first breakthrough in peace efforts in five years, has stalled as the sides disagree on who will control Hodeidah after the withdrawal. Hodeidah is of strategic importance because of its port, which is the entry point for some 80 percent of Yemen's imports and aid. In June, a Saudi-led coalition supporting the Yemeni government began a major offensive to seize Hodeidah, which has been under the control of rebels since Oct. 2014, a month after the Houthis overran the capital Sanaa.

Yemen lies beside the southern mouth of the Red Sea, one of the most important trade routes in the world for oil tankers. It has been wracked by conflict for the last five years when Shiite Houthi rebels overran much of the country. Saudi Crown Prince Mohammed bin Salman, the former Saudi defense minister, and Saudi Arabia's allies launched Operation Decisive Storm in March 2015. Civilians have borne the brunt of the conflict. The last available U.N. figure for the civilian death toll was published in 2016 and stood at more than 10,000. The Armed Conflict Location & Event Data Project, which tracks violence in Yemen, puts it at around 57,000 people.