If the warring parties in Yemen do not reach a peace agreement soon, the country could collapse with menacing consequences for the entire region, the UN humanitarian chief said Monday.

Stephen O'Brien told the Security Council that 80 per cent of Yemenis, some 21.2 million people, need some form of humanitarian assistance and over two million people, including 370,000 children, are suffering from malnutrition.

"The man-made brutal humanitarian disaster is now the catastrophe which I said was 'looming' in my first briefing to this council 18 months ago," O'Brien said. "It is high time that the parties put the Yemeni people first and reach a peaceful agreement in order to salvage what is left of the infrastructure, economy and social services of the country."

Complicating matters, the country now has 61 confirmed cases of cholera and 1,700 more suspected cases, O'Brien said.

O'Brien addressed the council by telephone from Bahrain to report on the dire situation in Yemen, which has been in the midst of a civil war since September 2014 when Shia Houthi rebels swept into the capital of Sanaa and overthrew the country's internationally recognized government.

The secretary general's special envoy to Yemen, Ismail Ould Cheikh Ahmed, said the security situation inside Yemen remains dire and that the humanitarian situation continues to deteriorate.

"Despite the international community's calls for the Yemeni parties to fully commit to the peace process, the parties continued to embark on unilateral actions which risk undermining the prospects for peace," Ahmed told the council.

He said he had been informed "unofficially" that the parties have rejected a proposed road map paving the way for a peace agreement and that he planned to head back to the region with the aim of reaching a detailed agreement based on the plan. He said it "provides a comprehensive solution and includes guarantees for the political representation of all political groupings."

"After 18 months of horrific fighting, thousands of deaths, injuries and unspeakable human suffering, we all need to ask how long will Yemenis remain hostages to personal reckless political decisions?" he asked. "What are the parties waiting for to sign a political agreement? Have they not understood there are no winners in wars?"