Four mobile cranes purchased by the United States arrived Monday at a rebel-held port in Yemen, the United Nations said, after months of delays imposed by the Saudi-led coalition.

The cranes will boost the capacity of the Huthi-controlled Hodeida port to receive food, fuel and medical supplies as Yemen remains on the brink of famine after nearly three years of war.

"This will allow for faster delivery of relief items for Yemeni families in the grips of the world's biggest hunger crisis," said UN spokesman Stephane Dujarric.

Coalition planes destroyed the cranes at Hodeida in a 2015 attack and Saudi Arabia has for months held up the delivery of the new cranes, which had been kept at a Dubai storage depot.

After a Huthi missile attack targeted Riyadh airport in November, the coalition shut down access to all airports and sea ports, including Hodeida.

UN officials say access for humanitarian deliveries remains a concern even if the blockade has been lifted.

US Ambassador Nikki Haley said in a statement that aid should be delivered to Yemen "without interference."

"No one should ever have to live the way the people of Yemen are living," she said.

With an offloading capacity of 66 tons (60 metric tons), the cranes will "significantly boost the discharge of humanitarian cargo," said Dujarric.

About 70 percent of Yemen's imports transit through Hodeida, which is also a key hub for aid deliveries. The coalition accuses rebels of using Hodeida to smuggle in weapons.

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.

A severe outbreak of cholera has left 2,000 dead and one million infected, according to the International Committee of the Red Cross.

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.

The war has had a heavy toll on civilians and UN efforts have failed to ease the conflict.