(CNN) -- European and American leaders weighed the pros and cons of arming Libya's rebels Wednesday -- a possibility made more urgent by a series of new military setbacks for forces seeking to topple strongman Moammar Gadhafi.
Government forces have been pushing from Bin Jawad to Ras Lanuf, a critical eastern oil town that the opposition seized on Sunday. Gadhafi's military has also launched escalated strikes in the western town of Misrata.
The new offensive was launched in the wake of an international arms embargo and air strike campaign designed to establish a no-fly zone and provide humanitarian relief for civilians threatened by the Libyan military.
British Prime Minister David Cameron told the House of Commons Wednesday that the United Nations Security Council mandate "allows all necessary measures to protect civilians and populated areas (and) this would not necessarily rule out provision of assistance to those protecting civilians in certain circumstances."
"As I've said before, we do not rule it out but we have not taken the decision to do so," he said.
U.S. President Barack Obama said Tuesday he is also open to the possibility of arming rebel fighters.
"I'm not ruling it out, but I'm also not ruling it in," he told NBC.
In a separate interview with ABC, Obama said that "if we wanted to get weapons into Libya, we probably could. ... We're looking at all our options at this point."
One significant problem, however, is the need to train opposition forces on how to use advanced weaponry.
"The notion of the gang that couldn't shoot straight might be lived out," retired Maj. Gen. James "Spider" Marks told CNN Tuesday night.
"There must be some degree of training associated with arming this force," said Marks, a former commanding general of the U.S. Army Intelligence Center. "However, some weapons systems, clearly they can get a handle on and they can use immediately. It's the more lethal weapon systems that would require training, and I don't think there's time to do that."
Another problem: a possible al Qaeda and Hezbollah presence within Libya's rebel movement. U.S. intelligence has detected evidence of "flickers" of al Qaeda and Hezbollah elements among the rebels, according to Adm. James Stavridis, the U.S. NATO commander.
Stavridis stressed Tuesday, however, that such a presence appears to be minimal.
"The intelligence that I'm receiving at this point makes me feel that the leadership that I'm seeing are responsible men and women who are struggling against Col. Gadhafi," Stavridis told a congressional committee.
Stavridis's comments come the same day that U.S. Secretary of State Hillary Clinton met with leaders of Libya's opposition in London.
A senior counterterrorism official, unnamed because he is not authorized to speak on the record, backed up Stavridis' assessment, downplaying the concern about al Qaeda among the Libyan opposition.
There is probably "a sprinkling of extremists to perhaps include al Qaeda" in Libya among the rebels, "but no one should think the opposition is being led by al Qaeda or one of its affiliates," the official said.
Al Qaeda has had a presence in North Africa for years.
"It's hard to tell who all the leaders are in the opposition," the official said, but "the rebels do not appear to be adopting an al Qaeda bent or ideology in Libya."
White House Press Secretary Jay Carney told reporters Tuesday that the rebel leaders meeting with Clinton "made clear what their principles are."
"We believe that (their principles are) meritorious," Carney said.
CNN's Reza Sayah, Alan Silverleib, Tom Cohen, Arwa Damon, Nic Robertson, Amir Ahmed, Paula Newton and Yousuf Basil contributed to this report