Yemen remains unstable and much more work needs to be done in the region, despite a declared halt to the Saudi-led bombing campaign in the country, the White House said on Wednesday.

"We strongly urge all Yemeni parties, in particular the Huthis and their supporters, to take this opportunity to return to these negotiations as part of the political dialogue," said NSC Spokesperson Bernadette Meehan.

"Having bravely and resolutely sought a democratic political transition, the Yemeni people deserve the opportunity to hold a peaceful debate about their new constitution, to participate in a credible and safe constitutional referendum, and to vote in free and fair national elections," she added.