The United States appears to be turning up the heat on Pakistan with intensified drone strikes and a cross-border NATO incursion since U.S. forces hunted down Osama bin Laden in the country, analysts and a Pakistani official said on Wednesday.
The pressure could further damage ties between the strategic allies, whose close cooperation is needed to stabilise neighbouring Afghanistan.
Since U.S. Navy SEALs killed bin Laden in a secret raid on May 2, Washington has been asking why he lived in Pakistan — by some accounts for up to five years — while Islamabad is furious about the operation, which it says violated its sovereignty.
"Drone attacks were taking place before, now there is more intensity," Rustam Shah Mohmand, Pakistan's former ambassador to Afghanistan, who is now an analyst, said.
"They now want Pakistan to finally go after the Taliban leaders they said are hiding in Pakistan." The United States is fighting Taliban insurgents in Afghanistan.
Tensions between Washington and Islamabad deepened on Tuesday.
NATO helicopters from Afghanistan opened fire at targets inside northwest Pakistan, wounding two soldiers, officials said, prompting a protest from the military already seething over the secret U.S. operation to kill bin Laden.
"I think they wanted to give us a message that they will do what they want," a senior security official told Reuters.
"We have clearly sent them message that things have changed after May 2. Intrusion isn't acceptable."
Mehmood Shah, former security chief of the country's tribal area on the Afghan border, said: "If the U.S. does not behave then there could be tough decisions by Pakistan."
But it is not clear how Pakistan could respond if the United States goes after another senior al Qaeda leader on its soil.
The unstable South Asian nation is heavily dependent on billions of dollars in U.S. aid. Some U.S. lawmakers angered by bin Laden's presence have called for a cut in those funds.
While relations were hurt by the bin Laden affair, analysts say neither side could afford to end a marriage of convenience.
"(Tuesday's) incident ultimately showed that neither side was willing to go the extent of attempting to decisively engage in a major confrontation with the other. At least, not yet," global intelligence firm STRATFOR said in a report.
"But one thing is certain: Pakistan is unlikely to be as accommodating to the United States as it has been in the past."
The drone strikes fuel anti-American sentiment, making it difficult for the United States to secure more help from the government.
Drone strikes have killed at least 37 militants in the past two weeks, Pakistani intelligence officials said. Militants often dispute official death tolls in the operations.
Washington has long demanded that Pakistan crack down harder on militants, especially Afghan Taliban fighters who cross the border to attack U.S.-led NATO troops in Afghanistan.
Pakistan is reluctant, analysts say, because it regards some of them as a counterweight to Indian influence in Afghanistan.
Pakistan's parliament passed a resolution last week that condemned the U.S raid on bin Laden's compound in the garrison town of Abbottabad, and threatened to stop NATO supplies to Afghanistan if drone attacks continued.
But few experts believe Pakistan can do that without facing serious consequences from Washington.
"U.S. pressure will continue, drone attacks will continue, border incursions will also continue, (Pakistani) protest will also continue, and some irritants would be caused," said Mohmand.
"But there will be no fundamental shift in policy, either in Islamabad or in Washington."
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