Libyan opposition forces are making major advances into Moammar Gadhafi's strongholds, but an American general said today that the rebels should slow down or they might get "destroyed."
Rebels recaptured two key oil facilities amid reports that this morning, they had taken control of Gadhafi's hometown of Sirte.
In the last 48 hours, rebels have blown through 300 miles of Gadhafi-held territory.
But U.S. Gen. Carter F. Ham issued a warning today to Libyan rebel forces.
"Among my concerns right now is that the opposition will over-reach in their haste to move west. They are not a match for the regime forces. If they move hastily and get destroyed. Then there's nothing to stop regime from moving right back down the coast road," he told ABC News.
If reports of the rebels' capture of Sirte are true, the development would be a major coup for the rebels who are quickly heading toward the capitol city of Tripoli. Sirte is halfway between the rebel-held east and the government-controlled west.
Watch ABC News for President Obama's speech on U.S. involvement in Libya, anchored by Diane Sawyer and George Stephanopoulos, live, Monday at 7:30 p.m. ET
The air raid on Tripoli began shortly after nightfall Sunday. Libyan state television confirmed air raids in Sirte and Tripoli.
Fighting started in the contested city of Misrata -- located between Sirte and Tripoli. Residents reported that pro-Gadhafi forces were firing on residential areas.
Gadhafi faces a larger coalition with NATO taking full command of both the no-fly zone and civilian protection.
According to Secretary-General Anders Fogh Rasmussen, NATO jets had already begun enforcing the no-fly zone Sunday.
"NATO allies have decided to take on the whole military operation in Libya under the U.N. Security Council resolution," Fogh Rasmussen said in a statement. "NATO will implement all aspects of the U.N. resolution. Nothing more, nothing less."
According to a senior Obama administration official who spoke on condition of anonymity, NATO will now assume the entire mission of implementing UN Security Council resolution 1973, which demands an immediate ceasefire in Libya, including an end to the current attacks against civilians.
This fulfilled President Obama's promise to take the leading edge with America's unique capabilities, and then quickly turn over authority to NATO, the official said.
More countries should be contributing assets to the operation, the official said, adding that not every country will have to take part in every aspect of the mission. While some may contribute to enforcing the arms embargo or the no-fly zone only, others may participate in bombings to protect civilians.
NATO will lead all of it, the official confirmed, stressing that the mission is to strike at anyone who targets civilians, not to support the Libyan rebels.
NATO commanders will have the authority to pick bombing targets and won't have to seek permission from a political body first, the official said.
Defense Secretary Robert Gates maintained said he could not provide a timetable for operations in Libya, according to the AP.
Speaking with ABC News' Jake Tapper on "This Week" Sunday, Gates said Libya presented no immediate threat to the United States.
"No, no -- it was not a vital national interest to the United States, but … the engagement of the Arabs, the engagement of the Europeans, the general humanitarian question, that was at stake," Gates said. "For all practical purposes, the implementation of a no-fly zone is complete. Now it will need to be sustained, but it can be sustained with a lot less effort than what it took to set it up," Gates said.
Appearing alongside Gates on "This Week," Secretary of State Hillary Clinton defended the mission in Libya while downplaying its length.
"I think that this had a limited timeframe, a very clearly defined mission, which we are in the process of fulfilling," Clinton said.
ABC News' Kirit Radia contributed to this report.