Yemen's rebels and government have agreed on a prisoner exchange that will reunite thousands of families, UN special envoy Martin Griffiths announced in Sweden on Thursday as representatives from both sides appeared in public together for the first time since civil war broke out in 2015. Speaking at the start of peace negotiations in Rimbo, a town north of Stockholm, Mr Griffiths said the government and the Houthis had signed "an agreement on the exchange of prisoners, detainees, the missing, the forcibly detained and individuals placed under house arrest". "It will allow thousands of families to be reunited, and it is the product of very effective, active work from both delegations," he said. The international Red Cross said it would oversee the implementation of the swap deal - the first formal memorandum between the Iran-backed rebels and Yemen's internationally recognised government, which is supported by a Saudi-led Arab coalition that includes the UAE. Meanwhile, UN Secretary General Antonio Guterres appealed to both Yemen’s government and the Houthis to make progress in the talks by “exercising flexibility and engaging in good faith and without pre-conditions”. “The Secretary-General appeals to the warring parties to continue the de-escalation in Hodeidah and explore other measures to mitigate the life threatening economic and humanitarian situation. He reminds the parties that a negotiated political settlement through inclusive intra-Yemeni dialogue is the only way to end the conflict and address the ongoing humanitarian crisis,” Mr Guterres’s spokesman told reporters in New York. Mr Griffiths said the coming days would be a "milestone" in which the two sides would have the opportunity to discuss a framework for “negotiation that sets the parameters for peace and the resumption of talks”. The talks are the first since UN-brokered negotiations in Kuwait in 2016 and come amid growing international concern about the humanitarian crisis caused by the war. More than 15 million people are in a "crisis" or "emergency" situation and that number could hit 20 million without sustained food aid, the UN's World Food Programme said on Thursday. About 65,000 people are at near famine levels, mostly in conflict zones, and the number could rise to 237,000 if aid does not get through, the WFP said, citing a survey of food security carried out by Yemeni and international experts in October. "We must find a solution on issues that will reduce the suffering, we will also discuss economic issues, the reduction of violence, and the re-opening of Sanaa airport," Mr Griffiths told the delegations in Sweden. <br/> Earlier on Thursday, he said sparing the port city of Hodeidah from destruction would also feature prominently at the peace talks. In an opinion piece in the<em> New York Times</em>, Mr Griffiths said disruption to the activities of Hodeidah port would spell disaster for millions. Both sides of the civil war have obstructed activities in the port, the main entry point for food and humanitarian aid. But with mounting US and UN pressure, the two sides have conceded that intensified clashes along the west coast of Yemen could greatly exacerbate an already dire humanitarian crisis. A ceasefire earlier this year brought temporary respite and allowed half a million residents to flee, leaving 150,000 in what used to be Yemen's fourth most populous city. Prior to the opening of the talks, an exchange of tweets between the two sides indicated a more aggressive tone than what Mr Griffiths had hoped to convey. The government demanded the rebels hand over Hodeidah port in accordance with a Security Council resolution. The “militias must withdraw from the west coast and hand it over to the legitimate government”, Foreign Minister Khaled Al Yamani said. In response, senior rebel leader Mohammed Ali Al Houthi said that if talks in Sweden failed to lead to a full opening of Sanaa airport, the Houthis would bar UN planes from using it. Mr Griffiths said the UN had received proposals from the government for reopening the airport in the rebel-held capital. "During the next few days we will be discussing it ... now we are together, I hope to make progress on this issue” he said. The prisoner swap deal was an auspicious start to the talks after Mr Griffiths succeeded in getting both parties to the venue and adhere to confidence-building measures - something he was unable to do on his last attempt in September. Both sides seem to be on the same page. Khalid Bin Salman, the Saudi ambassador to the US, announced his full support for Mr Griffiths shortly before returning to his post in Washington for the first time since being summoned to Riyadh after the murder of dissident journalist Jamal Khashoggi. <strong>_______________</strong> <strong>Yemen peace talks:</strong> <strong><a href="https://www.thenational.ae/world/mena/yemeni-government-delegation-arrives-in-sweden-for-peace-talks-1.799363">Yemeni government delegation arrives in Sweden for peace talks</a></strong> <strong><a href="https://www.thenational.ae/world/gcc/rebel-houthi-delegation-on-way-to-stockholm-for-peace-talks-1.798890">Rebel Houthi delegation on way to Stockholm for peace talks</a></strong> <strong>Editorial: <a href="https://www.thenational.ae/opinion/editorial/yemen-breakthrough-looks-closer-than-ever-1.799040">Yemen breakthrough looks closer than ever</a></strong> <strong>_______________</strong> Although many involved in the negotiations remain sceptical of a peace deal emerging from the talks, Mr Griffiths maintains that contact between the two parties brings them closer to a political agreement. "These political consultations in Sweden are the first step towards putting Yemen on the path to peace. I hope that by the end of this round, the Yemeni parties will agree on the outline of an eventual comprehensive agreement," Mr Griffiths said in his <em>New York Times</em> article. A UN spokeswoman told <em>The National</em> the talks were expected to go on for a week "but that all depends on what will happen the next few days". The last round of talks in 2016 continued for 100 days before the negotiations broke down in hostilities. “It’s been more than two years and it’s a hot war, building confidence is not easy, it’s a slow process - this morning I was contacted by leadership of the two sides urging me to work hard,” Mr Grifiths said. "We need to leave Sweden with some tangible outcome." Swedish Foreign Minister Margot Wallstrom opened the talks by wishing the two sides strength to find "compromise and courage" in their task.