Yemen's exiled government said on Tuesday it was ready to join U.N.-sponsored talks, but only if its Houthi adversaries publicly accepted a resolution calling on them to recognize the Yemeni president and quit Yemen's main cities.
The conflict has killed more than 4,500 people over nearly six months.
The United Nations envoy to Yemen, Ismail Ould Cheikh Ahmed, met Yemeni President Abd-Rabbu Mansour Hadi and his deputy, Khaled Bahah, in the Saudi capital Riyadh to try to kick-start the talks announced last week.
"If the Houthis are serious about sitting down for negotiations about implementing (U.N. Security Council) resolution 2216, they must publicly announce their recognition of this resolution," Yemeni government spokesman Rajeh Badi told Reuters by telephone from Riyadh.
The United Nations said last Thursday that peace talks to end the crisis were set to resume this week in the region and urged all parties to participate "in good faith."
But Hadi's office said on Sunday the government had decided not to join talks.
The exiled government's official news agency Saba said it would not join the U.N.-mediated talks until the Houthis accepted the April resolution.
Resolution 2216 calls on the Houthis to quit cities they had seized since September 2014 and to recognize Hadi as the legitimate president of Yemen.
The United Nations is trying to avert further bloodshed after the Saudi-led coalition and Hadi supporters began an offensive in Marib province east of Sanaa seeking to drive the Houthis out of the capital.
In New York, the U.N. special advisers on the prevention of genocide, Adama Dieng, and on the Responsibility to Protect, Jennifer Welsh, said recent developments "are likely to lead to escalation of the violence in central Yemen."
Hadi had been living in exile in Saudi Arabia since the Houthis advanced on his main stronghold in the southern city of Aden in March.
Badi said Ould Cheikh Ahmed had verbally conveyed to the Yemeni government the Houthis' acceptance of the resolution, apart from one article about sanctions.
"We are willing to go anywhere to negotiate for the implementation of resolution 2216, but we want to hear from the Houthis that they accept all 24 articles of this resolution," he said.
U.N.-sponsored talks in Geneva between the Yemeni government and the Houthis in June failed to achieve a breakthrough.
Hadi's supporters, backed by a Saudi-led coalition, have since made some gains against the Houthis and their ally, former President Ali Abdullah Saleh.
