The United States has suspended talks on normalizing relations with Sudan, saying neither the government nor regional leaders in the south are serious about ending a dispute over the Abyei region.

Announcing the suspension of the talks, U.S. special envoy to Sudan Richard Williamson said Tuesday that leaders of the north and south are, in his words, not interested in meaningful peace. He said he is leaving the country sad and disappointed.

In other developments, diplomats from the United Nations Security Council are in Sudan, trying to defuse the crisis over Abyei and its oil wealth. The Council has expressed concern the dispute could derail the 2005 peace agreement that ended Sudan's devastating north-south civil war.

The diplomats met Tuesday with southern Sudanese leader Salva Kiir, who is also Sudan's national vice president. Kiir accused the northern-based government of deploying more troops in Abyei.

He said if the troops continue to move to the area in large numbers it would be a violation of the 2005 peace agreement.

The U.N. team later flew to Khartoum, where they are expected to meet with Sudanese President Omar al-Bashir on Thursday.

Northern and southern Sudanese forces fought two rounds of clashes in the town of Abyei last month, killing dozens of people and displacing tens of thousands more. Witnesses say the town was virtually destroyed.

The United States has sanctions against various Sudanese officials and individuals because of alleged human rights abuses. The country is also on the U.S. list of state sponsors of terrorism.