VINEYARD HAVEN, Massachusetts - U.S. officials were in frequent contact Monday with Libyan rebels as they claimed control of most of the capital city of Tripoli. A top American diplomat said the whereabouts of longtime Libyan leader Muammar Qaddafi's were still unknown, but the U.S. Defense Department believes he is still in the country.
After the rebel's lightning advance on Tripoli, President Barack Obama urged Qaddafi to recognize his time is over in Libya. And Assistant Secretary of State Department Jeffrey Feltman said it was "only a matter of time" before the besieged ruler is history.
Still, Feltman acknowledged in an interview from Cairo Monday morning that U.S. officials do not know where Qaddafi is.
Defense Department spokesman Col. Dave Lapan said officials believe Qaddafi is still in the country. "We do not have any information that he has left the country."
Amid celebrations among rebels and sympathizers on the streets of Tripoli, Feltman said he thought it was "very clear that the rebels are winning."
"The rebels are taking over the city. They are clearly taking over the institutions," Feltman said in an interview on ABC television's "Good Morning America." He also said U.S. officials have been told the rebels have seized control of state television.
But Sunday's triumph may prove to be the easiest part in the rebels' quest to reshape Libya's political landscape.
Uniting to confront Qaddafi militarily is one thing, former diplomat Nicholas Burns told "The Early Show," but "it's much more difficult to organize effective government operation throughout a very vast country."
"The rebels have to unite the country politically, provide government services to a country that hasn't had it. That's a tall order. We can expect this to be chaotic, uneven and unfortunately violent as remaining Qaddafi supporters struggle against this rebel government," said Burns, who served as undersecretary of state during the George W. Bush administration and is now a professor at Harvard's John F. Kennedy School of Government.
Asked whether he believes the al Qaida terrorist network will gain new footing during a power vacuum in Libya, Feltman said the first step in any post-Qaddafi setting is to "prevent some kind of cycle where people act out their own retributions," as happened when Saddam Hussein fell in Iraq.
"A lot of that sectarian mix that existed in Saddam Hussein's Iraq doesn't exisit here in Libya," Feltman said. He also said that "the overwhelming vision that we are hearing" from people across Libya is that "they want a Libya that is moderate, that is secular."
An administration official said U.S. officials were talking regularly Monday with the rebel-led Transitional National Council, as well as U.S. allies around the world.
In Washington Monday, Pentagon spokesman Bryan Whitman said officials were carefully assessing developments.
"Clearly, there's a fluid situation," Whitman said. "We are monitoring the situation closely."
The Pentagon has provided well over 60 percent to 70 percent of the intelligence flights in support of NATO operations involving Libya. The U.S. led airstrikes before turning the mission over to NATO forces.
A vacationing Obama said in a statement from Martha's Vineyard, Massachusetts, Sunday night that Qaddafi should relinquish power to stop the violence and bloodshed of six months of civil war aimed at toppling his autocratic regime.
"The future of Libya is now in the hands of the Libyan people," Obama said. The U.S. has said that it would work closely with the rebels.
After a day of dramatic developments, Obama said the situation in Libya had reached a "tipping point" and control of the capital was "slipping from the grasp of a tyrant."
"The surest way for the bloodshed to end is simple: Moammar Qaddafi and his regime need to recognize that their rule has come to an end," Obama said. "Qaddafi needs to acknowledge the reality that he no longer controls Libya. He needs to relinquish power once and for all." Obama issued the statement after conducting a conference call with members of his national security team, who had provided him with updates throughout the day.
Clashes were reported early Monday near Qaddafi's compound in Tripoli when tanks rolled out and opened fire on rebels trying to storm the complex.