The United States government late Sunday repeated its conclusion that Libyan leader Moamer Gaddafi's grip on power is near an end, dpa reported.
"Gaddafi's days are numbered," US State Department spokeswoman Victoria Nuland said. "If Gaddafi cared about the welfare of the Libyan people, he would step down now."
An uprising broke out in February against his 42-year rule, and after a major offensive in the last week rebels claimed Sunday to be approaching Gaddafi's compound in Tripoli and to have captured two of his sons.
"We are closely monitoring the situation in Libya," Nuland said. "Clearly the offensive for Tripoli is underway."
US President Barack Obama and Secretary of State Hillary Rodham Clinton were being briefed regularly, she said.
The US is working to encourage the rebel leadership "to maintain broad outreach across all segments of Libyan society and to plan for post-Qadhafi Libya."