CAIRO — Yemen’s warring sides agreed on Thursday to exchange prisoners, starting peace consultations in Sweden that aim to end a conflict that has killed tens of thousands of civilians and pushed millions to the brink of famine.
The United Nations envoy to Yemen, Martin Griffiths, opened the talks, saying they represented a “critical opportunity” for Yemen. The prisoner exchange, said to involve at least 5,000 detainees, is the first of several confidence-building measures intended to draw the Houthi rebels and a Saudi-led coalition that supports President Abdu Rabbu Mansour Hadi into more substantive negotiations.
Also on the table is a proposal to reopen the airport in the capital, Sana, which has been under a Saudi blockade since 2015 — one of several punishing measures that have fueled what the United Nations calls the world’s biggest humanitarian crisis.
But hopes for the talks, which are taking place in a renovated castle north of Stockholm, are fragile. Numerous efforts to forge a cease-fire have crumbled, mostly recently in September, when a Houthi delegation failed to turn up in Geneva. Analysts have warned that another failure could set off even more intense fighting.
This time, however, the negotiations are being driven by a greater sense of international urgency.
The United Nations has issued dire warnings of potential famine in Yemen. In the United States, outrage over the killing of the Saudi dissident Jamal Khashoggi has increased broad pressure on the Trump administration to end military support.
It will be a delicate process. Initially, the rival delegations in Sweden will have no direct contact. Diplomats will shuttle between them in an effort to build common ground. Mr. Griffiths, the United Nations envoy, has said that the talks can succeed only if both sides “suspend their belief in the possibility of a military victory.”
Whether that is possible remains highly uncertain.
In the weeks before the talks, the United Arab Emirates, a key Saudi ally, pushed forward with a fierce offensive to snatch the Red Sea port of Hudaydah from Houthi control. Now coalition forces nearly surround the city, which is crucial to international aid efforts.
The United Nations hopes to broker a deal that would place Hudaydah under international control, effectively removing it from the strategic chessboard of the war and allowing relief to flow unimpeded into the country. The United Nations has warned that as many as 14 million people, or half the population of Yemen, could soon be dependent on that aid.
Whether either side is willing to compromise on the status of the city is likely to be a major point of contention.
For now, both sides are concentrating on less-contentious issues. The Red Cross said it had deployed a team to Sweden to help with the logistical details of the prisoner release, which is expected to involve 5,000 to 8,000 detainees.
“There is, I would say, an agreement in principle,” Fabrizio Carboni, the organization’s regional director for the Middle East, told reporters. “Now the discussion is at the technical level.”
A food survey published on Thursday by the United Nations, based on an international system for classifying famines, found that famine conditions already exist in pockets of Yemen.
At least 65,000 Yemenis are in a “catastrophic” situation, the survey found, and that number could rise to 237,000 if more aid does not get through soon, the World Food Program said in a statement.
The heads of five major aid organizations working in Yemen said last week in a strongly worded joint statement that responsibility for ending the suffering lay in large part with the Trump administration, owing to its staunch support of Saudi Arabia.
“We cannot escape the truth: if it does not cease its military support for the Saudi/U.A.E. coalition, the United States, too, will bear responsibility for what may be the largest famine in decades,” the leaders of Oxfam, Care, the International Rescue Committee, Save the Children and the Norwegian Refugee Council said in the statement.
The peace talks in Sweden are scheduled to last one week. At the opening ceremony, where the rival camps sat opposite each other for the first time in two years, Sweden’s foreign minister, Margot Wallstrom, wished them the strength to find “compromise and courage” in the days ahead.
“Now it is up to you, the Yemini parties,” she said. “You have the command of your future.”