A nearly two-month lull in American drone strikes in Pakistan has helped embolden Al Qaeda and several Pakistani militant factions to regroup, increase attacks against Pakistani security forces and threaten intensified strikes against allied forces in Afghanistan, American and Pakistani officials say.

The insurgents are increasingly taking advantage of tensions raised by an American airstrike in November that killed two dozen Pakistani soldiers in two border outposts, plunging relations between the countries to new depths. The Central Intelligence Agency, hoping to avoid making matters worse while Pakistan completes a wide-ranging review of its security relationship with the United States, has not conducted a drone strike since mid-November.

Diplomats and intelligence analysts say the pause in C.I.A. missile strikes,  the longest in Pakistan in more than three years, is offering for now greater freedom of movement to an insurgency that had been splintered by in-fighting and battered by American drone attacks in recent months. Several feuding factions said last week that they were patching up their differences, at least temporarily, to improve their image after a series of kidnappings and, by some accounts, to focus on fighting Americans in Afghanistan, a report in The New York Times said on Sunday.

The spike in violence in the tribal areas, up nearly 10 percent in 2011 from the previous year, according to a new independent report, comes amid reports of negotiations between Pakistan’s government and some local Taliban factions, although the military denies that such talks are taking place.

A logistics operative with the Haqqani  group, which uses sanctuaries in Pakistan to carry out attacks on allied troops in Afghanistan, said militants could still hear drones flying surveillance missions, day and night. “There are still drones, but there is no fear anymore,” he said in a telephone interview. The logistics operative said fighters now felt safer to roam more freely.

Over all, drone strikes in Pakistan dropped to 64 last year, compared with 117 strikes in 2010, according to The Long War Journal, a Web site that monitors the attacks. Analysts attribute the decrease to a dwindling number of senior Qaeda leaders and a pause in strikes last year after the arrest in January of Raymond Davis, a C.I.A. security contractor who killed two Pakistanis; the Navy Seal raid in May that killed Osama bin Laden; and the American airstrike on Nov. 26.

 “It makes sense that a lull in U.S. operations, coupled with ineffective Pakistani efforts, might lead the terrorists to become complacent and try to regroup,” one American official said. “We know that Al Qaeda’s leaders were constantly taking the U.S. counterterrorism operations into account, spending considerable time planning their movements and protecting their communications to try to stay alive.”

C. Christine Fair, an assistant professor at Georgetown University who just returned from a month in Pakistan, put it more bluntly: “They’re taking advantage of the respite. It allows them to operate more freely.”

Several administration officials said Saturday that any lull in drone strikes did not signal a weakening of the country’s counterterrorism efforts, suggesting that strikes could resume soon. “Without commenting on specific counterterrorism operations, Al Qaeda is severely weakened, having suffered major losses in recent years,” said George Little, a Defense Department spokesman. “But even a diminished group of terrorists can pose danger, and thus our resolve to defeat them is as strong as ever.”

Analysts say the hiatus coincides with and probably has accelerated a flurry of insurgent activity and new strategies.

In telephone interviews, some Pakistani militants said the purpose of the agreement with Afghan Taliban was to settle internal differences among rival factions and improve the image of the Taliban, which has been tarnished because of the increasing use of kidnapping and the rise in civilian killings.

Other analysts say that the Afghan Taliban are also feeling the pinch of American-led night raids and other operations across the border. They said the Taliban needed the militants in Pakistan’s tribal region to focus more on helping to launch a final offensive in Afghanistan, in hopes of gaining leverage before any peace talks and the ultimate withdrawal of most American forces from Afghanistan by 2014.

One of the main drivers of the accord was Sirajuddin Haqqani, the leader of the Haqqani network, prompting some Pakistani analysts to reason that the Pakistani Army had also prodded the creation of the council, or shura, to maintain its leverage in any peace negotiations.

“No agreement is ever permanent in frontier politics, and it’s all very complicated,” said one American government official with decades of experience in Pakistan and its tribal areas.

In a sign of the shifting insurgent tactics, the number of suicide bombings in the country declined to 39 through November, compared with a high of 81 in all of 2009, according to the Pakistani military.

The number of attacks from homemade bombs, however, increased to 1,036 through November, compared with 877 for all of 2009. More than 3,500 Pakistani soldiers and police officers have been killed since 2002.

One senior Pakistani Army officer with experience in the tribal areas said that insurgents had devised increasingly diabolical triggers and fuses for bombs.

Unlike Americans, Pakistani soldiers still drive in pickups or carriers with little protection. “The effects are devastating,” said the officer, who spoke on the condition of anonymity. “Vehicles are basically vaporized.”

“The Pakistani Army is overstretched, and that’s clearly had an impact on morale,” said Maleeha Lodhi, a former Pakistani ambassador to the United States. “But we have to maintain the pressure on the militants.”