The UN Security Council is preparing a resolution that could order sanctions against figures seeking to undermine Yemen's state-building drive, diplomats said Tuesday.
Work on the resolution is still at an early stage but some countries want former president Ali Abdullah Saleh named in the document, diplomats said.
The 15-nation Security Council held talks Tuesday on Yemen's just-finished national conference on drawing up a new constitution.
Council president Prince Zeid al-Hussein, Jordan's UN envoy, said the body is "ready to take measures" against those who act against the conference, but did not mention the proposed resolution.
"The council is united," added the prince.
The UN's special representative to Yemen, Jamal Benomar, told reporters he had warned the council of the threats to the country's transition from the "former regime."
Saleh stood down as president in February 2012 after a year of popular protests.
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The national conference, which ended Saturday, laid the foundations for a federal state -- welcomed by the United States and European Union -- but the country has been rocked by deadly unrest.
"Yemen is the only negotiated transition in the context of the Arab spring and now the country where the most genuine transparent and inclusive national dialogue has taken place," Benomar said, praising the conference.
"Undoubtedly there is real progress in the transition and the beginning of a new political culture in Yemen, yet the situation remains fragile," he added.
"Elements of the former regime continue to maneuver to obstruct, to frustrate and undermine the course of change, aiming to set back and bring down the transition," he said, without mentioning specific names.
He added he had briefed the council "on this systematic pattern of obstruction which constitutes a genuine threat that could plunge the country into chaos if the threat is not removed soon."
Diplomats said talks would start soon on the resolution, which could be voted in February.
"The aim is to include sanctions but there is no decision yet on which names should be included," said one UN diplomat.
"It is clear that Saleh is involved and some countries want him and other members of his regime specifically named," said another envoy.