The United Nations on Tuesday dismissed a Saudi demand that tighter inspections be put in place at Yemens rebel-held Hodeida port before a devastating blockade is lifted.
The Saudi-led coalition fighting rebels in Yemen shut down the country's land, sea and air borders a week ago in response to a missile attack by the Iran-backed Huthis that was intercepted near Riyadh.
The UN has warned that an already catastrophic humanitarian crisis in Yemen was worsening each day that aid shipments remained blocked.
Saudi Arabia's ambassador to the UN Abdallah al-Mouallimi told reporters in New York on Monday that ports in government-controlled areas such as Aden, Mukalla and Mocha will be reopened, but demanded more rigorous checks at the Red Sea port of Hodeida.
The UN's aid coordinator in Yemen, Jamie McGoldrick, said there was no time to wait for a new inspection system to be set up.
"The humanitarian impact of what is happening here right now is unimaginable," he told reporters in Geneva in a phone conference.
"I don't think discussions (on new inspections) should hamper the port remaining open", he added.
"The humanitarian aspect of this is something we need to address immediately because we can't have those ports closed or those airports closed while we wait for discussions on new (inspection) mandates to go ahead."
McGoldrick underscored that UN aid was the main lifeline for most of Yemen's population, seven million of whom are at risk of famine.
He said that a UN verification and inspection mechanism already in place could work with the Saudi-led coalition on implementing new procedures but that keeping ports closed in the interim was not viable.
Stocks of diesel and petrol are running out in parts of Yemen because of the blockade, while the prices of basic goods have skyrocketed.
The blockade "is complicating what is already a catastrophic situation", McGoldrick said.
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.