The UN special envoy to Yemen held talks Sunday with the country's warring parties in a bid to break an impasse, a day after the government pulled out of direct negotiations.

Ismail Ould Cheikh Ahmed held separate morning talks in Kuwait City with delegates, and plenary or committees' meetings were planned in the afternoon, spokesman for the UN envoy Charbel Raji said.

Yemen's government on Saturday pulled out of direct negotiations with representatives of the Huthi rebels after there were no signs of any progress.

A source close to the government delegation said the talks had reached a delicate stage after "the rebels backtracked to the starting point".

"That has complicated the situation," the source told AFP, requesting anonymity.

The rebels and their allies have demanded the formation of a consensus transitional government before forging ahead with other issues that require them to surrender arms and withdraw from territories they occupied in 2014.

The rebels have also demanded the withdrawal of a small US force operating in the south of the country against Al-Qaeda militants.

On Thursday, Ould Cheikh Ahmed said the foes had begun discussing major political and security issues in face-to-face negotiations aimed at bringing an end to 13 months of devastating war.

The working groups exchanged views on resolving political and security issues and the release of prisoners and detainees, in accordance with UN Security Council Resolution 2216.

This orders the rebels to withdraw from territory they have taken since 2014 and to surrender heavy weaponry they had seized.

There has been mounting international pressure to end the Yemen conflict that the United Nations estimates has killed more than 6,400 people and displaced 2.8 million since March last year.