Yemen's warring parties welcomed a UN call for an immediate truce on Thursday as the country entered its sixth year of a conflict that has unleashed a humanitarian crisis, rendering it more vulnerable to any coronavirus outbreak.

A Saudi-led military coalition said late on Wednesday it backed the Yemeni government's acceptance of the UN appeal. The Iran-aligned Houthi movement welcomed that stance but said it wants to see implementation on the ground.

The US Agency for International Development (USAID) meanwhile said it had started to reduce aid to areas controlled by the Houthis, on concerns the group hinders the delivery of assistance, a spokesperson said.

The new coronavirus has yet to be documented in the impoverished Arabian peninsula nation where conflict violence has killed more than 100,000 and left millions on the brink of starvation.

Following his call for a global ceasefire to focus on combating the pandemic, UN Secretary-General Antonio Guterres on Wednesday urged Yemen's parties to end hostilities and restart peace talks last held in December 2018.

The Arab coalition supports efforts for a ceasefire, de-escalation, confidence-building measures and work to prevent a coronavirus outbreak, spokesman Colonel Turki Al Malki said.

"The coalition's announcement ... is welcome. We are waiting for it to be applied practically," a senior Houthi official, Mohammed Ali Al Houthi, tweeted on Wednesday.

Yemen had witnessed a lull in military action after Saudi Arabia and the Houthis launched back-channel talks late last year. But there has been a recent spike in violence that threatens fragile peace deals in vital port cities.

"We have a global coronavirus pandemic threatening to overwhelm an already broken healthcare system," said Tamuna Sabadze, country director at the International Rescue Committee, adding that Yemen was already battling a large cholera outbreak.