The US officials say that parts of the Pakistani military and intelligence services are mounting this campaign and this extends to refusal to extend approved visas for more than hundred American officials and frequent searches of US diplomatic vehicles in major cities, the New York Times reported quoting US officials.

The harassment affects military attache's, CIA officers, junior level diplomats, development experts and others. And as a result, the Times said, some key American aid programmes to Pakistan are grinding to a halt.

The delays in granting visas extensions are even affecting military programmes as scores of US helicopters being used by the Pakistan Army in its ongoing campaign against the Taliban can no longer be serviced as the specialists have not been given visas.

The paper said reimbursement to Pakistan of nearly USD one billion a year for counter-terrorism has been suspended because the last of the American embassy's five accountant had to leave the country after their visas expired.

"There’s an incredible disconnect between what they want of us and the fact we can’t get the visas," a diplomat said.

Pakistani officials acknowledged the situation but said the menacing atmosphere resulted from American arrogance and provocations, like taking photographs in sensitive areas, and a lack of understanding of how divided Pakistanis were about the alliance with the United States.

The campaign comes after months of rising anti-American sentiment here and complaints by the military that the government of President Asif Ali Zardari has grown too dependent on a new USD 7.5 billion, five-year aid plan from Washington.

A Pakistani security official, who has kept a tally of many of the incidents, was not sympathetic, saying the Americans had brought on the problems.

It also appears to be an attempt to blunt the planned expansion of the United States Embassy to 800 Americans from 500 in the next 18 months, growth that American officials say is necessary to channel the expanded American assistance.

"They don’t want more Americans here," another American diplomat said. "They’re not sure what the Americans are doing. It’s pretty pervasive."

The harassment has grown so frequent that American officials said they viewed it as a concerted effort by parts of the military and intelligence services that had grown resentful of American demands to step up the war against the Taliban and al-Qaeda.

Though the United States has been sending large amounts of military assistance to the Pakistani Army, and helping its premier spy agency, the Inter-Services Intelligence directorate, the campaign shows the ambivalence, even "hatred" toward the United States in those quarters, the American official said.

The Pakistani security official said the Americans were arrogant. "They think of themselves as omnipotent. That’s how they come across."
The searching of American diplomatic vehicles at the many checkpoints in the cities has become one of the biggest irritants.

But the US says that its diplomats behaving in a high-handed manner are all false.
An American embassy official cited a recent report in some Pakistani newspapers that an US diplomat had been taking photographs in a military area of the city of Lahore.

He said the suspected diplomat, a technical support officer, was not carrying a camera.
In another instance, the Pakistani security official said, Americans in an S.U.V. last week fled after the police tried to search their car at a checkpoint on the outskirts of the capital.

The embassy spokesman denied that Americans had fled the checkpoint. "Nonsense, diplomats don’t run away," he said.

Because diplomatic license plates registered to the embassy would provide an easy target for militants, the Americans reached an accord some time ago with Pakistan’s government that their official plates would be carried inside the car, the spokesman said.

But the absence of plates left the American cars vulnerable to searches at checkpoints, he said. Under international conventions diplomatic cars are not subject to searches, and American diplomats were instructed not to permit searches beyond opening the trunk, the spokesman said.

At least 135 American diplomats have been refused extensions on their visas, the senior American diplomat said, leaving some sections of the embassy operating at 60 percent of capacity.

Much of the heightened suspicions about American diplomats appears to revolve around persistent stories in the Pakistani press about the presence of the American security company Blackwater, now called Xe Services, in Pakistan, the report said.