World powers sought Tuesday to persuade Yemen's Houthis to send representatives to peace talks in Kuwait as a truce teetered near collapse, delegates said.
Houthi negotiators have stayed put in Sana'a, which their movement holds, demanding a cease-fire that began April 10 be fully observed before they travel for the talks. Plans had called for the sessions with representatives of President Abdu Rabu Mansour Hadi's government to start Monday.
The Houthis have also rejected a proposed agenda that stipulates they hand over heavy weapons and withdraw from areas they control before a new government comprising all Yemeni forces is formed.
A failure of the talks is likely to stoke fighting between the Iran-allied Houthis and their ally, former President Ali Abdullah Saleh, on the one side and Hadi supporters, backed by a Saudi-led Arab coalition, on the other.
An adviser to the U.N. delegation in Kuwait said the Houthis had been "very positive" until two days ago and had agreed with envoy Ismail Ould Cheikh Ahmed on almost everything.
"They have since completely changed, and this has caused a shock," the aide, who asked not to be identified, told Reuters.
The envoy was now working with the Houthis and the government to iron out the problems.
Appeal from Ban
U.N. Secretary-General Ban Ki-moon appealed to all Yemeni parties to engage with Ould Cheikh Ahmed "so that talks can start without further delay."
A Western diplomat said the Chinese ambassador to Yemen delivered a message from the five permanent members of the U.N. Security Council to the Houthis that urged them to attend the talks.
"We understand your concerns but you need to carry your worries to Kuwait and put them at the table," the diplomat said, quoting the message.
Hadi's government ordered its delegation to stay put in Kuwait while the United Nations sought to persuade the Houthis to join the talks.
Meanwhile, residents in Marib province, east of Sana'a, reported intensified fighting after troops loyal to Hadi arrived Monday, having trained in Saudi Arabia. Fighting was also taking place in Taiz in southwestern Yemen despite the presence of cease-fire monitors, while Saudi-led warplanes flew over Sana'a.
The Houthis have observed a period of calm along the border with Saudi Arabia and exchanged prisoners with Riyadh, paving the way for Ould Cheikh Ahmed to draft a broad outline for the talks.
The United Nations says the Yemen war has killed more than 6,200 people and displaced millions in the poorest country in the Arabian Peninsula. Al-Qaida and Islamic State have also exploited the war to widen their influence and gain more supporters in a country next door to Saudi Arabia, the world's top oil exporter.
The Houthis complain that Hadi's forces are trying to exploit the truce to try to make gains on the ground in several provinces, while warplanes from the Saudi-led alliance continued to fly over areas held by the group.
Teams of joint cease-fire monitors have been deployed in some areas, but the Houthis say they were still unable to curb continued violations of the truce.
Houthi spokesman Mohammed Abdul-Salam said Monday that the movement had long been ready for a dialogue to bring peace to Yemen and stability to the entire region, but the violence had not stopped with the cease-fire.
Abdul-Salam said one of the committees set up to monitor the cease-fire in the northern al-Jawf province had had a lucky escape from an airstrike by the Saudi-led coalition.
Abu Malek al-Feeshi, another prominent Houthi leader, criticized the U.N. envoy, accusing him of presenting contradictory drafts for peace talks. He said in a Facebook post that his group was ready for peace "at any venue and at any time" as soon as the fighting stopped.