The call for the unconditional ceasefire comes a week after a Saudi-led campaign against the Houthi rebels targeted a funeral hall in Yemen's capital Sanaa.
The United States and Britain have called for an immediate cessation of hostilities in Yemen, where the conflict between Houthi rebels and the exiled government has triggered a massive humanitarian crisis
The call for the urgent and unconditional ceasefire comes a week after a Saudi-led campaign against the Houthis targeted a funeral hall in Yemen's capital Sanaa.
The air strike by the Saudi coalition, which is backing the government in the conflict, killed 140 people and sparked an international outcry. It raised also questions about the continued military and financial support to the Saudi coalition by the US and Britain.
On Sunday, US Secretary of State John Kerry said there was an urgent need to end the conflict in Yemen "as rapidly as possible, meaning Monday, Tuesday".
"This is the time to implement a ceasefire unconditionally and then move to the negotiating table," Kerry said after meeting the United Nations envoy to Yemen and his opposite numbers from Britain, Saudi Arabia and the United Arab Emirates at talks hosted by Britain in London.
Kerry would not predict whether Yemen's government or rebel forces had accepted the demand, but said the diplomats were not operating "in a vacuum."
The UN envoy, Cheikh Ahmed, echoed Kerry's words, saying he had been in contact with the Houthi militia's lead negotiator and with Yemeni President Abedrabbo Mansour Hadi's government.
But he also warned that he hoped for "clearer plans" for a ceasefire in coming days.
Yemen's war has intensified since UN-sponsored peace talks in Kuwait ended in August without an agreement. Fighting has been concentrated around the country's Houthi-controlled ancient capital, Sanaa, where little territory has changed hands.
With food ships finding it hard to get into Yemen's ports due to a virtual blockade by the Saudi-led coalition during the 18-month civil war, over half the country's 28 million people are facing severe food shortages, according to the UN.
British Foreign Secretary Boris Johnson said the conflict in Yemen was "causing increasing international concern; the fatalities that we're seeing there are unacceptable".
The conflict has killed close to 10,000 people, wounded more than 35,000 and displaced at least three million since March last year, according to the United Nations.