The UN-brokered power transition deal that eased president Ali Abdullah Saleh out of office a year ago after three decades in power and following protests calls for the national dialogue to produce a new constitution and electoral law.
"The transition is threatened by those who have still not understood that change must now occur," the UN envoy to Yemen Jamal Benomar told the UN Security Council.
He warned that opponents of the dialogue were "keen to impede this transition and to profit from instability".
"Many Yemenis expect the Security Council to keep a careful watch on the spoilers' actions and to hold them accountable," Benomar added.
The envoy urged the Yemeni government to "take confidence-building measures to address the grievances of the southerners" and thus provide an environment that could foster talks.
The national dialogue conference, originally scheduled to take place in mid-November, has been delayed after factions in the Southern Movement, which has campaigned for autonomy or outright secession for the formerly independent south, refused to join the talks.
After North and South Yemen unified in 1990, the south broke away in 1994. The move sparked a short-lived civil war that ended with the region being overrun by northern troops.
Technical and logistical help
Benomar met with Southern Movement leaders in Cairo recently to prod them to participate in the national dialogue. And the UN Secretary-General Ban Ki-moon visited Sanaa last month promising technical and logistical help from the world body.
"The road towards fresh elections may seem long and difficult," Benomar said.
And despite progress made toward normalization, the envoy noted that integrating military and security forces under a single command will remain a "formidable task" and a "serious challenge."
During the Security Council debate, several Western ambassadors also joined Benomar's calls for talks to begin soon.
"There is a genuine risk of the government not being prepared in time" for elections expected in 2014, British envoy Mark Lyall Grant said in calling for the national dialogue to begin this year and include both women and all political parties.
"We see negative actions from certain individual, spoilers who wish to derail the political transition," he added.
Yemenis must hold the national dialogue based on the Gulf and UN-brokered power transfer deal in which President Abdrabuh Mansur Hadi replaced Saleh.
The talks are intended to result in a new constitution and prepare for legislative and presidential elections at the end of Hadi's two-year interim period in February 2014.