The rebels were finally set to join talks on Tuesday afternoon as they arrived a day late after being stranded in Djibouti -- a fact they blamed on Riyadh.

But rebel negotiating team member Mohammed Zubairi defiantly told reporters: "We refuse any dialogue with those who have no legitimacy."

He said they instead wanted talks with Saudi Arabia, which has been leading an aerial campaign against the rebels since March 26, "to stop the aggression".

The United Nations is desperately trying to get the rebels, who control a large swath of terrain including the capital Sanaa, and the exiled government to agree to a badly-needed humanitarian truce.

But any hope of a thaw appeared bleak with exiled president Abedrabbo Mansour Hadi repeating Tuesday that his side was only prepared to discuss with the rebels a Security Council resolution ordering their withdrawal from seized territory.

A UN-chartered plane carrying the rebels had left Sanaa on Sunday afternoon but was forced to wait in Djibouti for nearly 24 hours, forcing them to miss Monday's opening of the talks and a meeting with UN chief Ban Ki-moon.

The rebels accused Egypt and Sudan of not allowing their plane to fly through their airspace.

"It was Saudi Arabia which asked its allies" to take the action with the aim of "torpedoing the negotiations", Adel Shujah, another member of the rebel team, told AFP after arriving in Geneva.

He said they were able to travel on to Switzerland after the United States and Oman intervened.

Oman is the only Gulf monarchy that has not joined the Saudi-led coalition fighting the rebels. Oman maintains good relations with both Iran and Saudi Arabia.

Yemen has been wracked by conflict between Iran-backed Shiite rebels and troops loyal to Hadi, who fled to Saudi Arabia in February.

Global powers are keen for a speedy resolution, fearing the growing power of Al-Qaeda in the Arabian Peninsula, the Yemeni branch of the jihadist network that has taken advantage of the chaos to seize territory.

On Monday, Ban underscored the need for an immediate humanitarian truce in Yemen for at least two weeks to mark the holy Muslim month of Ramadan in order to furnish critical supplies to millions of people facing acute shortages.

The UN has described Yemen's humanitarian crisis as "catastrophic", with 80 percent of the population -- 20 million people -- in need of aid.

The UN children's agency said Tuesday that at least 279 children had been killed in Yemen since the Saudi-led strikes began -- a figure four times higher than for the whole of last year.

Robert Mardini, who heads the International Committee of the Red Cross' Middle East operations added that there was currently "little hope for the people of Yemen where dozens are being killed every day."

The rebel team is expected to join the talks on Tuesday afternoon but there are outstanding issues, including the rebels' inflated presence, UN spokesman Ahmad Fawzi said.

He said before the rebels joined the talks, the UN wanted to ensure they adhered to "the 7+3 principle, that is seven principals and three advisers" on the negotiating team.

However, the rebels appear to have turned up with a much more substantial entourage.

Both experts and some participants are pessimistic about the outcome of the talks. The positions of the two warring sides are so divergent that they will not be sitting in the same room and the UN will be holding separate consultations with them.

The rebels are supported by military units loyal to ex-president Ali Abdullah Saleh.

The second day of the talks coincide with reports, confirmed by Al Qaeda in Yemen, that its leader Nasir al-Wuhayshi, number two in the global jihadist organisation, was killed in a US drone strike.