A closure of the Hodeida port would "bring disaster to Yemen," which is already on the brink of famine, the new head of the UN's World Food Programme warned Wednesday.
There are rising fears that a Saudi-led military coalition fighting rebels in Yemen could attack the Hodeida port, through which most of the country's food is imported.
A spokesman for the coalition however has denied it plans to launch an offensive on Hodeida.
"Ninety percent of the imports into Yemen come in through the port of Hodeida. Something like 80 percent of all the World Food Programme food comes through that port," David Beasley told AFP.
"So if that port is shut down for whatever reason, it would bring disaster to Yemen."
Hodeida, in the west of the country, is currently controlled by the Iran-backed Huthi rebels that the Saudi-led coalition is battling.
The UN, along with aid and rights groups, has warned that a military offensive against the port would be "devastating".
"If that port gets closed down, the risk of famine substantially increases," said Beasley.
"Let's pray and hope that doesn't happen."
Yemen, already one of the poorest countries in the Arab world, has suffered a downward spiral in living conditions during years of conflict, with the UN warning earlier this year that a third of its provinces were on the brink of famine.
In the two years since the Saudi-led intervention began, more than 7,700 people have been killed and around three million displaced, according to the United Nations.
Beasley said the WFP was doing contingency planning in case Hodeida became inaccessible, but said any alt ernative would stretch already limited funds.
"Obviously we are doing everything we can to search for alternatives -- how do we use other ports and access cross-border lines, airlifts, drops, every imaginable possibility," he said.
"But then the cost goes up at least 10 times... in a country (for which) we have only about 25 percent of the funds we need."
"We're on the brink of famine in Yemen, and every day that passes... that we do not have a political solution is another day closer to famine."
The UN says 17 million Yemenis -- or around 60 percent of the population -- are unable to access food.
"Children and men and women are dying now," Beasley said.
"It hasn't reached... the accepted definition of a famine. But it's knocking on the door and time is running out."