The coalition closed all air, land and sea ports last week in response to a rebel ballistic missile attack on Riyadh.
The Saudi-led coalition hopes that will prevent "the smuggling of weapons, ammunitions, missile parts and cash that are regularly being supplied by Iran and Iranian accomplices to the Houthi rebels", the statement said.
The UN's World Food Programme warned that current stocks of rice will run out in 111 days and wheat in 97.
"The space and access we need to deliver humanitarian assistance is being choked off, threatening the lives of millions of vulnerable children and families".
After two years of a devastating war, the Houthis still control much of Yemen's north while the south falls under the embattled President of Abed Rabbo Mansour Hadi, whose government is recognized by the global community and who is supported by the Saudi-led coalition.
UN Still Can Send Humanitarian Flights to Sanaa Airport After Recent Strike
The war has killed more than 10,000 people and displaced 3 million. "There are many sources of supply to Yemen, even during the past week or so". The UN has called it the "worst humanitarian crisis in the world".
Pressing the Government in the House of Lords, Lord Ashdown of Norton-sub-Hamdon said: "Even allowing for the fact of jihadist terrorism, is not the greatest threat to peace coming from the Middle East now the imminent danger of a conflict between the Sunnis and the Shias, led by Saudi Arabia and Tehran, in which the West is backing one side and Russian Federation the other?"
A malnourished Yemeni child receives treatment at a hospital in the port city of Hodeida on November 05, 2017.
The U.N. says Secretary-General Antonio Guterres has written to Saudi Arabia's U.N. ambassador saying the kingdom's failure to reopen key Yemen airports and sea ports is reversing humanitarian efforts to tackle the crisis in the impoverished country.
"We have some 21 million people needing assistance and seven million of those are in famine-like conditions and rely completely on food aid", United Nations humanitarian coordinator for Yemen Jamie McGoldrick said.
Dujarric says the United Nations urges the coalition to resume U.N. humanitarian flights to Aden and the capital, Sanaa, and to reopen the ports of Hodeida and Salif for food and medical deliveries.