NEW YORK - Shifting tactics, the United States has backed away from further commando ground raids into Pakistani territory after furious complaints from its government, and is relying instead on intensified air strikes, The New York Times reported Monday. Citing American and Pakistani officials, the newspaper said attacks by remotely piloted Predator aircraft have increased sharply in frequency and scope in the past three months. There have been at least 18 Predator strikes since the beginning of August, some deep inside Pakistan's tribal areas. The US has also been praising Pakistan's stepped up military operations against them and for refusing to enter into dialogue with them. "They (Pakistanis) have shown more fight than ever before," an unnamed State Department official was quoted as saying by the Times. "They show no desire to negotiate with the militants." However, other officials were quoted as saying that by relying on air strikes alone, the United States would not be able to weaken al-Qaeda's grip in the tribal areas permanently. Within the government, advocates of the ground raids have argued if the US can successfully capture suspected Qaeda leaders by just sending Special Operations forces into Pakistan, the paper said. The decision to focus on an intensified Predator campaign using Hellfire missiles appears to reflect dwindling options on the part of the White House for striking al-Qaeda in the Bush administration's waning days, it added. After months of debate within the administration and mounting frustration over Pakistan's failure to carry out more aggressive counter terrorism operations, President Bush finally gave his approval in July for ground missions inside Pakistan. But the only American ground mission known to have taken place was a Special Operations raid on September three, in which the roughly two dozen people killed including some civilians, it said, adding that American officials say there has not been another commando operation since. Pakistani President Asif Ali Zardari has vowed zero tolerance against violations of his country's sovereignty amid the strikes, which have stoked anti-US sentiment in Pakistan. According to the newspaper, following the attack, Pakistani National Security Adviser Mahmud Ali Durrani made an unannounced visit to Washington and expressed his country's anger in person to top White House officials, including National Security Adviser Stephen Hadley. But while ground raids have stopped, attacks by remotely piloted Predator aircraft, which are operated by the Central Intelligence Agency, have increased sharply in the past three months, the report said. Quoting a senior US official, the Times reported that there is no tacit agreement with Pakistan to allow increased Predator strikes in exchange for stopping ground raids, which too remains an option on the table. On Pakistani side, it said, officials have publicly stated that they regard the Predator attacks as a less objectionable violation of Pakistani sovereignty. Husain Haqqani, Pakistan's Ambassador to the US, told the Council on Foreign Relations this month that the two nations were cooperating in deploying "strategic equipment that is used against specific targets". "There's always a balance between respecting full Pakistani sovereignty, even in places where they're not capable of exercising that sovereignty, and the need for our force protection," an unidentified US administration official was quoted as saying by the Times. Attacks by militants, ensconced in Pakistan havens, against US and allied forces in Afghanistan, have increased by about 30 per cent from a year ago, according to US military officials. In response, the CIA has expanded its list of targets in Pakistan and has gained approval from the government there to bolster eavesdropping operations in the border region, according to US officials, the Times said. Many of the Predator strikes are taking place as deep as 25 miles into Pakistani territory. Targets include not just Al Qaeda leaders but also Pakistani militants, even trucks carrying rockets to resupply fighters in Afghanistan. A Predator strike in South Waziristan on Oct 16 killed Khalid Habib, a senior Al Qaeda operative. But the strikes sometimes have unintended consequences. On Sept 8, one in Miranshah on a compound owned by a Taliban leader, Jalaluddin Haqqani, failed to kill him but did kill women and children, the Times noted. Talking about the achievement of the increased airstrikes, a Western counterterrorism official told the Times: 'It's fair to say that it has caused key Al Qaeda figures to focus even more on their safety and security. It has caused them to be more suspicious of people they don't know well, and it also has caused frictions between Al Qaeda and tribal elements.' But the official acknowledged that the intensified operations have so far failed to shake Al Qaeda's hold on the tribal areas.