Libya's interim rulers are reported to have sent more fighters toward one of Muammar Qaddafi's last strongholds, Bani Walid.
Officials from the interim ruling National Transitional Council (NTC) said they had sent reinforcements after reports that Qaddafi had issued a call for the town to fight.
Talks with Qaddafi backers on an orderly surrender of Bani Walid, a city of 100,000 residents some150 kilometers south of Tripoli, have so far failed.
Meanwhile, the NTC has sent envoys to neighboring Niger to try to stop Qaddafi and his entourage evading justice.
A convoy arrived in Niger this week, but Niger says Qaddafi was not in it.
The Pentagon said it had no information to indicate the fallen leader had left Libya.
State Department spokeswoman Victoria Nuland urged Libya's neighbors to be vigilant should Qaddafi supporters try to flee across their borders.
"We're calling on all of these countries to make every effort to control their borders, to detain any Qaddafi regime officials, to confiscate contraband, any illegal weapons, and disarm them, and also to confiscate any wealth that might properly belong to the Libyan people," Nuland said.
Elsewhere, the head of the UN watchdog monitoring chemical weapons said he believed Libya's remaining chemical weapons are secure despite the instability there since the uprising started in February.
Ahmet Uzumcu, director general of the Organization for the Prohibition of Chemical Weapons, also said his inspectors are ready to return to Libya to oversee the destruction of Qaddafi's poison gas supplies as soon as conditions will allow it.
compiled from agency reports