The UN mediator travelled Saturday to Aden in south Yemen to press for the government and Shiite rebels to open long-delayed peace talks on December 12, a Yemeni official said.
Ismail Ould Cheikh Ahmed met President Abedrabbo Mansour Hadi, who has declared the port city Yemen's provisional capital following the rebels' capture of Sanaa and other regions over the past year.
The official close to the president said the envoy left after a brief visit.
"Mr Ould Cheikh Ahmed is seeking the agreement of President Hadi to convening the talks in Geneva on December 12," he told AFP.
But the mission was "difficult", said the source, accusing the rebels of dragging their feet on implementing UN Security Council Resolution 2216, which calls for them to withdraw from occupied territory.
And Foreign Minister Abdel Malak al-Mekhlafi told AFP: "The putschists are refusing to lay down their arms or to allow the government to carry out its duties" from Sanaa.
"They have not announced their list of negotiators" for the talks "and are trying to escalate the situation on the ground by bombing residential districts of Taez", a strategic city in southwest Yemen under siege by the rebels and their allies, he said.
In a protest sent to the United Nations, Yemen's minister in charge of human rights, Ezzedine al-Isbahi, condemned the "massacres and atrocities" allegedly committed in Taez by the rebels that he said had killed 33 civilians last week, including four children.
Mekhlafi denounced the Huthis and their allies for having filed a lawsuit on Wednesday in Sanaa against Hadi and his aides over their request for a Saudi-led military intervention that had "damaged the independence" of Yemen.
The United Nations says that more than 5,700 people have been killed in Yemen, almost half of them civilians, since a Saudi-led air campaign began in March in support of the government.
In Aden, meanwhile, gunmen shot dead the presiding judge of a terrorism court, Mohsen Mohamed Alwan, and four of his bodyguards, a security source said, and police Colonel Al-Khadher Ali Ahmed was gunned down in a separate attack.