The representatives of Yemen's warring parties have met on a ship in the Red Sea to discuss the stalled truce agreement for the contested port city of Hodeidah.
Retired Dutch General Patrick Cammaert chaired the meeting on board a United Nations' vessel off the Yemeni coast on Sunday after the Houthi rebels refused to hold talks in government-held areas.
The discussions will continue on Monday, a UN statement said, describing the meeting as "cordial and constructive".
Cammaert "warned the parties about the fragility of the ceasefire and urged them to instruct their commanders on the ground to refrain from any further violations that would jeopardise the Stockholm Agreement and the broader peace process for Yemen", the statement said.
A Saudi-UAE coalition of forces has been fighting Houthi rebels for control of the country since 2014.
As the negotiations took place, reports emerged that the deputy chief of staff of the Saudi-backed Yemeni government died from wounds sustained last month in a drone attack by Houthis on the country's largest airbase, Al Anad, while a military parade was under way.
That attack came after a truce was agreed to in December in Sweden that included a ceasefire in rebel-held Hodeidah, a pullback of forces from the port city, and the opening of humanitarian corridors.
The UN is overseeing the implementation of the ceasefire and troop withdrawal in Hodeidah, the main entry point for most of Yemen's imports, in the hope it will lead to a political solution to the almost four-year war.
Dispute over control
Each side has repeatedly accused the other of violating the ceasefire.
The warring parties were meant to withdraw their forces by January 7 as part of efforts to avert a full-scale assault on Hodeidah, but have failed to do so as the Iranian-aligned Houthi group and the Saudi-backed government disagree on who should control the city and ports.
"The problem with this particular settlement is political," said Al Jazeera's Hashem Ahelbarra, who has reported extensively from Yemen.
"It's more now about who is the legitimate authority. The government is saying 'we are the only sole legitimate authority recognised by the international community'. The Houthis say, 'we are the de facto political establishment in the country because we are the ones who in 2014 made the difference'."
Sunday's meeting was the third time the UN-led Redeployment Coordination Committee convened since it was formed in December, bringing together the Houthis with the internationally recognised Yemeni government and UN mediators.
The first two meetings were held in territory under Houthi control and Cammaert - the head of the UN mission tasked with overseeing the deal - shuttled between the two parties.
Yemen, one of the Arab world's poorest countries, has been embroiled in a power struggle between the government and the Shia Houthi rebels since late 2014.
The conflict, widely seen in the region as a proxy war between Saudi Arabia and Iran, has been bogged down in a military stalemate for years.
'Respect' for ceasefire
A coalition led by Saudi Arabia and the United Arab Emirates intervened in Yemen in 2015 to try to restore the government of Abd-Rabbu Mansour Hadi after it was thrown out of power in the capital Sanaa by the Houthis in late 2014.
The Houthis, who say they are enacting a revolution against corruption, control most urban centres in Yemen while Hadi's government controls the southern port of Aden and string of coastal towns.
Over the past four years, the conflict has led to mass displacement, food shortages and outbreaks of cholera and diphtheria across the country, as well as damage to healthcare and education infrastructure.
Pope Francis on Sunday called for urgent "respect" for a ceasefire accord in Yemen to allow humanitarian aid through in the conflict-weary country.
"I appeal to all parties concerned and to the international community to allow the urgent respect of established accords to ensure the distribution of food and to work for the good of the population," said the pope.
"I am following the humanitarian crisis in Yemen with great concern," he added.
Francis was speaking before embarking on an historic three-day visit to the UAE, the first by a pope to the Arabian Peninsula.
A rights group has urged the pontiff to use the visit to highlight the UAE's role in abuses during the war in Yemen.
In a letter to Pope Francis, Human Rights Watch (HRW) cited the UAE's "prominent" role in the Saudi-led alliance and alleged the "coalition has indiscriminately bombed homes, markets, and schools, impeded the delivery of humanitarian aid, and used widely banned cluster munitions".
The group said it documented nearly 90 attacks, some likely war crimes, and called on the pope to look into the allegations.
"We urge you to use this upcoming visit to press the UAE to investigate alleged serious violations by its armed forces and Yemeni forces it supports, to appropriately prosecute those responsible for war crimes, and to provide reparation to victims of violations," HRW said.