Addressing the Security Council, Martin Griffiths said a possible sharp escalation from the missile attacks on Saudi Arabia and intensified fighting could "in a stroke, take peace off the table."

"My plan is to put to the council within the next two months a framework for negotiations," Griffiths said in his first council report since taking over as special envoy in February.

The Saudi-led coalition battling Yemen's Huthi rebels on Monday warned it was ready to inflict a "painful" response if new attacks are carried out against Saudi Arabia.

Riyadh said last week it had shot down two Iran-supplied drones in the south of the kingdom as well as interceptws ballistic missiles fired from rebel-held parts of Yemen, the latest in a series of similar incidents.

Griffiths cited the increased number of ballistic missile launches, intensified military operations in northwest Saada governorate, ongoing air strikes and movements of forces in the Hodeidah region as worrisome developments.

"Our concern is that any of these developments may, in a stroke, take peace off the table. I am convinced that there is a real danger of this," said the envoy.

War-wracked Yemen is the world's worst humanitarian crisis, according to the United Nations, with 75 percent of the population -- 22 million people -- in need of aid, seven million of whom are at risk of famine.

More than 9,200 people have been killed since the Saudi-led alliance joined the Yemen war, according to the World Health Organization.

A severe cholera outbreak has also killed 2,000 people and infected one million, the International Committee of the Red Cross said.