GENEVA (AP) -- The United Nations humanitarian aid chief says he doesn't expect an "easy or rapid process" in peace talks that begin this week involving warring sides in Yemen, which faces the world's largest humanitarian crisis.
A Yemeni rebel official said, meanwhile, the country's internationally recognized government and its allies in a Saudi-led coalition have signed a U.N.-brokered prisoner exchange deal with the Shiite rebels.
Mark Lowcock, head of the world body's Office for the Coordination of Humanitarian Affairs, spoke to The Associated Press on Monday after laying out the organization's 2019 humanitarian appeal. He said the "onus" in the peace talks is on Yemen's government and Iran-aligned rebels to "take this seriously and act in a responsible way."
Rebel delegates were expected to fly to Stockholm from neighboring Oman on Wednesday, while other delegates were to head there from Sanaa later Tuesday or Wednesday.
OCHA says $21.9 billion is needed next year for food, shelter, health care, education, protection and other assistance. It predicts nearly 132 million people in 42 countries will need assistance.
The appeal says Yemen "is closer to famine than ever before."
The Yemeni rebel official, Abdul-Qader el-Murtaza, said late Monday that U.N. envoy Martin Griffiths informed the rebels that the coalition and the government have signed a prisoner exchange deal nearly three weeks after the rebels did.
The move meets one of the conditions set by the rebels to participate in U.N.-mediated peace talks due to start in Sweden this week, the latest diplomatic bid to end Yemen's civil war.
The U.N. has said both sides agreed to attend the talks.