Moamer Gaddafi is running out of time as the NATO military campaign intensifies and the Libyan leader's forces have come under "tremendous strain," the White House said Tuesday, dpa reported.
"The trends show that time is very much working against Gaddafi," Ben Rhodes, the deputy national security advisor for communications, said in London, where Obama is due to meet with British Prime Minister David Cameron on Wednesday.
Rhodes cited the massive NATO airstrikes on command and control centres in Tripoli on Tuesday, and the ability of the rebel opposition - with NATO support - to hold back Gaddafi's forces at Misurata, Ajdabiya and Benghazi, the rebel stronghold in eastern Libya.
"We believe that Qaddafi and his forces are under tremendous strain," Rhodes said.
The situation in Libya is expected to be high on the agenda during Obama's meeting with Cameron, as some British and French politicians have been clamoring for the US to play a greater role in NATO's mission.
The British and French are reported to be considering sending in helicopter gunships to enable NATO to carry out lower level ground assaults.
The US played the lead role in the initial strikes on Libya that began on March 19 by launching hundreds of Tomahawk missiles against Libyan air defences and command and control facilities. The strikes were meant to make it safe for NATO planes to enforce a UN-backed no-fly zone and protect civilians.
The US transferred control of the mission to NATO at the end of March but has continued to provide broad logistical support, including "unique" capabilities like targeting intelligence, aerial refuelling and jamming Libyan air defences, Rhodes said.
Rhodes gave no indication that the US was willing to expand its role on a routine basis, saying Obama made it clear to Cameron and French President Nicolas Sarkozy that the US commitment would be limited and NATO partners would have to take overall responsibility for the mission.
"That was the understanding from the beginning," Rhodes said. "What we've said since then is that we would consult with NATO, consider requests, but that the nature of our commitment was always going to be limited in scope and duration."