A Houthi delegation arrived in Sweden on Tuesday for UN-sponsored peace talks, the first since 2016, as Western nations press for an end to the war in Yemen amid warnings from the United Nations of a looming economic disaster.

The Houthi team was escorted from the capital Sana'a, which was seized by the group in 2014, to Sweden by UN special envoy Martin Griffiths. Before boarding a Kuwaiti plane, one delegate praised him for making good on confidence-building measures like the evacuation of wounded fighters and a prisoner swap deal.

Yemen's Saudi-backed government is expected to follow the Houthis, whose attendance was secured after the evacuation of 50 of their injured militants for treatment in Oman on Monday.

A previous round of peace talks in September collapsed when the Houthis failed to appear.

The talks will be held in a renovated castle outside Stockholm to discuss further confidence-building steps and a transitional governing body, as the U.S. Senate is set to consider a resolution to end support for the coalition in the war.

Yemen's Saudi-backed government and the Houthis have agreed earlier to exchange hundreds of prisoners ahead of the planned peace talks, according to media reports. The deal would cover between 1,500 and 2,000 members of the pro-government forces and between 1,000 and 1,500 rebels, a government official said.

The nearly four-year-old conflict in Yemen has killed thousands and spawned the world's most urgent humanitarian crisis. The United Nation appealed for four billion U.S. dollars in aid to Yemen on Tuesday.

UN aid chief Mark Lowcock said Yemen's government will need billions of dollars in external support to finance its 2019 budget and avoid another currency collapse in addition to the aid.

Oil revenues, the main source of government income, had declined about 85 percent.

"The country with the biggest problem in 2019 is going to be Yemen," Lowcock said.