The United Nations warned Wednesday that fuel supplies needed to run Yemen's hospital generators and pump clean water will run out in less than three weeks unless the Saudi-led coalition lifts its blockade.

The dire forecast came as Yemen battles one of the world's worst outbreaks of cholera, with nearly one million people infected. Some 2,200 people have died.

Adding to the woes of aid workers on the ground, stocks of diphtheria vaccines will be emptied in two weeks unless aid deliveries are once again allowed in the country, UN spokesman Farhan Haq said.

The Saudi-led military coalition shut down Yemen's sea and air ports as well as borders on November 6 in response to a missile attack by the Iran-backed Huthi rebels near Riyadh.

UN aid chief Mark Lowcock warned last week that unless the blockade was lifted, Yemen will face "the largest famine the world has seen for many decades, with millions of victims."

A week after hearing that dire warning, the UN Security Council appeared powerless on Wednesday to push the Saudi-led coalition to lift its blockade of humanitarian aid.

"There are still huge problems and there has not been any progress on the... open humanitarian access through the ports of Hodeida and airport of Sanaa," both held by the rebels, said Olof Skoog, the Swedish ambassador to the United Nations.

Sweden, a non-permanent council member, called for a council meeting last week on the crisis, but Skoog did not indicate whether he will seek another meeting on the aid blockade.

"We are concerned that not enough has happened," he said. "We'll see what the next step will be on that."

The United Nations has listed Yemen as the world's number one humanitarian crisis, with 17 million people in need of food, seven million of whom are at risk of famine.

Last week, Egypt, a non-permanent council member close to Saudi Arabia, circulated a draft statement that condemned the missile attack on Riyadh but made no mention of the aid blockade.

Diplomats criticized the proposed statement as lacking balance and said they did not expect it to be endorsed by the council.

UN aid officials meanwhile have stepped up their appeals.

"The humanitarian impact of what is happening here right now is unimaginable," said the UN's aid coordinator in Yemen, Jamie McGoldrick, this week.

The World Food Programme has warned that current stocks of rice will run out in 111 days and wheat in 97 days, while the prices of basic goods have skyrocketed.

Saudi Arabia and its allies intervened in Yemen in March 2015 to push back the Iran-backed Huthi rebels who control the capital Sanaa, and restore the government of President Abedrabbo Mansour Hadi to power.