Benghazi, Libya (CNN) -- The CIA is operating in Libya to help the United States increase its "military and political understanding" of the situation, a U.S. intelligence source said Wednesday.

"Yes, we are gathering intel firsthand and we are in contact with some opposition entities," the source told CNN.

The White House refused to comment on a Reuters report Wednesday that President Barack Obama has signed a secret order authorizing covert U.S. government support for rebel troops.

"I will reiterate what the president said yesterday -- no decision has been made about providing arms to the opposition or to any group in Libya," said White House press secretary Jay Carney in a statement. "We're not ruling it out or ruling it in. We're assessing and reviewing options for all types of assistance that we could provide to the Libyan people, and have consulted directly with the opposition and our international partners about these matters."

Meanwhile, another senior Libyan official broke Wednesday with Libyan leader Moammar Gadhafi, whose loyalist forces have opposition fighters on the run after a string of successes.

And members of Congress questioned administration officials as to why they weren't asked to authorize Obama's decision to commit U.S. forces.

According to the Reuters report, Obama signed the covert aid order, or "finding," within the past few weeks. Such findings are required for the CIA to conduct secret operations, the report said.

A U.S. official not authorized to speak publicly could not confirm the finding but noted when there are crises like this, "you look at all instruments of national power."

In early March, a U.S. official told CNN "the intelligence community is aggressively pursing information on the ground" in Libya.

There has been growing discussion over whether the coalition will arm the opposition and provide training on the use of effective weapons systems.

British Prime Minister David Cameron told the House of Commons on Wednesday that he has not ruled out arming the Libyan opposition, but added that Britain has not made the decision to do so.

U.S. Defense Secretary Robert Gates and Secretary of State Hillary Clinton provided classified briefings to House and Senate members who asked whether the United States intended to arm the Libyan rebels, participants told CNN.

Clinton and Gates made clear that no decision had been made on arming the rebels, with Congress members from both parties saying they believed it would be a bad idea, according to participants.

Regarding the committing of U.S. forces to the U.N.-backed operation, the White House has said Obama acted within his authority under the War Powers Act. It notes that the president and other officials consulted congressional leaders several times in the run-up to the March 19 deployment of U.S. forces to the U.N.-authorized Libya mission.

Legislators from both parties said after Wednesday's House briefing that Clinton told them the administration acted within the requirements of the War Powers Act and needed no congressional authorization for further decisions on the mission.

Rep. C.A. "Dutch" Ruppersberger, D-Maryland, ranking member of the House Intelligence Committee, would not discuss whether Obama signed the aid order.

"From an intelligence perspective, we have one of the most superior intelligence operations in the world and that is a resource that we use throughout the world to protect us and protect allies," Ruppersberger told CNN.

Libyan Foreign Minister Moussa Koussa arrived in London Wednesday and told the government there that he has resigned, the United Kingdom Foreign Office said.

CNN's Ben Wedeman, who has been reporting from Libya for several weeks, said that Koussa's departure is a significant blow, but not a critical loss to the regime.

A Foreign Office spokesperson said Moussa was one of the most senior figures in Gadhafi's government "and his role was to represent the regime internationally -- something that he is no longer willing to do."

The department provided no other details.

Libya's opposition said its fighters are executing a "tactical withdrawal" from a swath of territory they once controlled, a move that comes as Gadhafi's forces relentlessly pound them.

Col. Ahmed Bani, speaking at a news conference in the opposition capital of Benghazi on Wednesday, said his forces are being outgunned by the superior military power of loyalists, spared the wrath of coalition airstrikes.

They have been pushed eastward over the last two days after CNN reported on Sunday that rebels took Brega, Ras Lanuf and Bin Jawad and reached a town just east of Sirte.

Rebel forces have now lost Bin Jawad and the key oil town of Ras Lanuf and are backed up to the Brega area, Bani said. Ajdabiya, which is east of Brega, will be prepared as a "defense point" if the withdrawal continues farther east, he said.

Opposition leader Bani called on the international community to supply opposition fighters with better and more powerful weapons to hold off the Gadhafi forces. He said the opposition was open to foreign troops training rebel fighters. Bani asked for tanks, heavy artillery, and communications and logistics equipment.

The rebels have been demanding an end to Gadhafi's almost 42-year rule in Libya, but they have been facing "sustained attacks in the face of the coalition bombing" in Misrata, Ras Lanuf, and Bin Jawad, CNN's Nic Robertson reported.

In an address to the House of Commons in London on Wednesday, British Foreign Secretary William Hague said that "regime forces have intensified their attacks, driving back opposition forces from ground they had taken in recent days." He cited the violence in the western town of Misrata.

"Misrata also came under heavy attack yesterday, with further loss of civilian life, including children, from mortars, sniper fire and attacks on all sides from regime tanks and personnel carriers," Hague said.

In the outskirts of Ajdabiya -- which was recently taken over by opposition forces -- Gadhafi's regime planted several dozen land mines, Human Rights Watch said in a statement Wednesday.

"Given the pedestrian and vehicular traffic in the area, the mines were clearly laid while government forces were in Ajdabiya," the group said.

Human Rights Watch also said 370 people are missing in the eastern part of the country, with some suspected to be in government custody. That list includes rebel fighters and civilians, including doctors, the group said.

Addressing the specter of civilian casualties during warfare, Hague said he received a letter from the local council in Misrata thanking the allies for the targeted strikes and the no-fly zone, and he said the group confirmed "that there has been not a single case of civilian injury, let alone death, in and around Misrata."

CNN's Robertson said the Libyan government has been saying there have been dozens of civilian casualties but hasn't been able to prove it.

However, during a government-controlled tour of a hospital on Wednesday, he saw one woman with a broken leg, apparently injured by shrapnel after a missile strike.

"This is the first person we have seen who does appear to have injuries consistent with what the government has told us, as a result of coalition strikes," Robertson said.

In the woman's account, a coalition missile struck an ammunition dump close to where she lived. She described rushing out of the house to see what was happening. She was injured when she went back in and a missile hit the dwelling.

Cell phone video from her brother also "seems to be consistent" with the account, and journalists have reported that strike.

Bani, meanwhile, also rejected a U.S. military official's allegation that some al Qaeda elements or fighters were among the opposition forces.

"We don't have this kind of fundamentalism thinking or attitude, so it's not in our part to be organizing al Qaeda fighters in our ranks," Bani said. He said any Libyan fighters who may have previously had links to al Qaeda have cut those ties and are now fighting to liberate Libya.

Bani said three sources told him that soldiers from neighboring Chad's Republican Guard are fighting as mercenaries for the Gadhafi regime, describing 3,200 to 3,600 "mercenaries and militiamen" from the country.

this problen in lybia is a big ptoblem