In a bid to save the CIA's drone campaign against al-Qaida in Pakistan, US officials offered key concessions to Pakistan's spy chief that included advance notice and limits on the types of targets. But the offers were flatly rejected, leaving US-Pakistani relations strained as President Barack Obama prepares to meet on Tuesday with Pakistan's prime minister.

CIA Director David Petraeus, who met with Pakistan's then-spy chief, Lt. Gen. Ahmed Shuja Pasha at a meeting in London in January, offered to give Pakistan advance notice of future CIA drone strikes against targets on its territory in a bid to keep Pakistan from blocking the strikes - arguably one of the most potent U.S. tools against al-Qaida.

The CIA chief also offered to apply new limits on the types of targets hit, said a senior US intelligence official briefed on the meetings. No longer would large groups of armed men rate near-automatic action, as they had in the past - one of the so-called 'signature' strikes, where CIA targeters deemed certain groups and behavior as clearly indicative of militant activity.

Pasha said then what Pakistani officials and its parliament have repeated in recent days: that Pakistan will no longer brook independent US action on its territory by CIA drones, two Pakistani officials said. All the officials spoke on condition of anonymity to discuss the sensitive negotiations.

Pasha went further, saying Pakistan's intelligence service would no longer carry out joint raids with U.S. counterterrorist teams inside its country, as it had in the past. Instead, Pakistan would demand that the U.S. hand over the intelligence, so its forces could pursue targets on their own in urban areas, or send the Pakistani army or jets to attack the targets in the tribal areas, explained a senior Pakistani official.

The breakdown in US-Pakistani relations follows a series of incidents throughout 2011 that have marred trust - from a CIA security officer who shot dead two alleged Pakistani assailants, to the US Navy SEAL raid that killed Osama bin Laden in May, to the border incident where US forces returned fire they believed came from a Pakistani border post, killing 24 Pakistani troops. The diplomatic fallout has led to the ejection of US military trainers who'd worked closely with Pakistani counter-insurgent forces, slowed CIA drone strikes, and almost halted the once-common joint raids and investigations by Pakistan's intelligence service together with the CIA and FBI.

Pasha's pronouncements were in line with the Pakistani parliament's demands issued last week that included ceasing all US drone strikes as part of what Pakistani politicians call a 'total reset' in its relationship. Pakistan's parliament last week demanded cessation of all unilateral US actions including the drone strikes.

The rejection of the US offers set up a potentially rocky meeting ahead between Obama and Pakistani Prime Minister Yusuf Raza Gilani in South Korea on Tuesday, on the sidelines of the Nuclear Security Summit. President Asif Ali Zardari met with special representative to Afghanistan and Pakistan Ambassador Mark Grossman en route to Pakistan, and Central Command chief Gen. James Mattis is headed to Pakistan in April.

Complicating efforts to restore relations are the demands made by a Pakistani parliamentary committee.

A personality change at the top of the Pakistani Inter-Services Intelligence is another wrinkle, with Pasha now replaced by Army Lt. Gen. Zaheerul Islam officially last week, a senior U.S. official said. While Islam has spent time studying at U.S. military institutions, and once served as deputy to the ISI, he is a mostly unknown quantity to US officials. The staff change was not anticipated when the January Pasha-Petraeus meeting took place, both US and Pakistani officials said.

The diplomatic furor threatens to halt the CIA's drone program, which in the last eight years, has killed an estimated 2,223 Taliban, al-Qaida and other suspected militants with 289 strikes, peaking at 117 strikes throughout 2010, reducing al-Qaida's manpower, firepower and reach, according to Bill Roggio at the Long War Journal website, which tracks the strikes. US officials say his figures are fairly accurate, though they would not give more precise figures.

The strikes have markedly slowed to only 10 strikes in the opening months of this year, with the last in mid-March, Roggio said. That puts the program on pace for a total of 40-50 strikes for the year, less than the year before.

Roggio says the strikes so far this year seem to back up that report: out of the 10 strikes, two killed high-value targets, and another strike killed three mid-level Taliban leaders, with no large groups reportedly targeted by any of the drone's missiles. In previous years, an average of only 5 percent to 10 percent of targets were deemed high value, with larger numbers of foot soldiers and a much lower percentage of commanders among those hit.

US officials took issue with the interpretation that signature strikes had ceased, adding the "US is conducting, and will continue to conduct, the counterterrorism operations it needs to protect the US and its interests." The CIA offered no official comment.

In his opening salvo to keep the program going, Petraeus offered to give his Pakistani counterpart advance notice of the strikes, as had been the practice under the Bush administration, which launched far fewer strikes overall against militant targets.

The US had stopped giving the Pakistanis advance notice, after multiple incidents of targets escaping, multiple senior US counterterrorist officials say. U.S. intelligence intercepts showed Pakistani officials alerted local tribal leaders of impending action on their territory, and those leaders oftentimes in turn alerted the militants.

Petraeus also outlined how the US had raised the threshold needed to take strikes, requiring his approval more often than in the past, the US official said.

Pakistan's military wants to go back to the "Reagan rules - the way the CIA operated with the ISI against the Soviets" inside Afghanistan, says former CIA officer Bruce Riedel, of the Brookings Institute. "We give them a big check, and they make every decision about how that is spent. Minimal American footprint in country, or involvement in actual fighting the bad guys."

"We cannot trust the ISI to fight this war for us," after finding bin Laden in a Pakistani military town, "showing the ISI was either clueless or complicit," Riedel said.