Yemen's Zaidi Shia Houthi rebels have rejected President Abdrabbuh Mansour Hadi's nomination for prime minister.
A decree appointed Ahmed Awad bin Mubarak to the post, but rebels said the matter was "under consultation".
Last month, the Houthis signed an agreement with Mr Hadi to try to end a political crisis that saw some of the worst violence for years in Sanaa.
The president reversed unpopular fuel subsidy cuts and gave the rebels a say in the formation of a new government.
It was hoped that by naming prime minister acceptable to the Houthis, its fighters could be persuaded to leave the capital.
The presidential decree was issued after meetings between Mr Hadi and several advisers, including representatives of the rebels.
The official Saba news agency claimed that Mr Mubarak's appointment was met with agreement from all parties.
However, rebel spokesman Abdul Malik al-Ijri said that his group did not agree with the appointment and that consultation on a new prime minister was still ongoing.
The fighting in Sanaa last month, which came after weeks of protests and clashes, threatened to derail the UN-backed transition to democracy launched after President Ali Abdullah Saleh was forced to step down in 2011.
The Houthis, also known as Ansar Allah (Partisans of God), have staged periodic uprisings since 2004 to win greater autonomy for their northern heartland of Saada province.
Timeline: Recent key events
29 July - Government removes fuel subsidies as part of economic reforms; fuel prices nearly double
18 Aug - Houthis set up armed protest camps in Sanaa
31 Aug - Houthi leader calls for campaign of civil disobedience
2 Sept - President agrees to dismiss government and promises to review subsidy cuts - Houthis reject move
10 Sept - Security forces shoot dead seven Houthi protesters outside cabinet building
18 Sept - Clashes between Houthis and Sunni militias in Sanaa leave 40 dead
21 Sept - Houthis occupy key buildings in Sanaa; PM resigns; deal for new unity govt signed