The Pentagon believes Libya's Muammar Gaddafi has not fled the country, a military spokesman said, as rebel forces continued their sweep of the capital.

It's "probably fair to stay that we believe he's still in the country," spokesman Colonel Dave Lapan told reporters.

"We do not have information that he's left the country."

He said the US military was cotninuing to provide support for the NATO-led air campaign over Libya as the situation in Tripoli was "fluid".

Gaddafi's exact whereabouts remained unclear, he said.

Amid speculation about a possible international peacekeeping mission, Lapan ruled out the deployment of any US ground troops as part of a UN or NATO post-Gaddafi peacekeeping force.

"There will not be US boots on the ground," he said.

"If there's going to be some type of transitional mission, that remains to be seen, whether it comes out of the UN or NATO.

"But we still do not plan any US forces going on the ground in Libya."

The United States has contributed aircraft mainly for refueling and surveillance flights for the NATO campaign, launched in March, as well as armed Predator drones.