ISLAMABAD – ISI DG Lieutenant General Zaheer ul Islam on Monday postponed a visit to the United States in the latest sign of tensions between the two allies struggling to get their relationship back on track.

Pakistan and the United States have been at loggerheads over Pakistan’s six-month blockade on NATO supplies for Afghanistan and last week’s sentencing of a Pakistani doctor hired by the CIA to help find Osama bin Laden.

While intelligence cooperation has continued, Lieutenant General Zaheer ul Islam’s decision not to accept a tentative invitation from CIA director David Petraeus this month was unlikely to be viewed favourably by all in Washington.

In a short message, the Inter Services Public Relations (ISPR), communication wing of the Pakistan armed forces, said only that the visit by the Inter-Services Intelligence director general had been “postponed due to his pressing commitments here”.

“There is no other reason of postponing the visit,” a spokesman said.

Frustrations have been growing in Pakistan and the United States on how to break the impasse over the NATO supply lines, US drone strikes on Pakistani soil and last week’s conviction of treason for Shakeel Afridi.

Relations went into free fall last year, first when a CIA contractor shot dead two Pakistanis, then over the US raid that killed bin Laden on May 2, and lastly over US air strikes that killed 24 Pakistani soldiers in November.

After the air strikes, Pakistan shut its Afghan border to NATO supplies and agreed to reset relations on condition that Washington apologise for the soldiers’ deaths and end drone attacks.

But five US drone strikes have been reported since a NATO summit in Chicago last week failed to secure a deal on resuming the supply lines, the most dramatic increase in attacks since parliament demanded in March that they stop.

Two attacks on Monday alone killed at least nine militants in North Waziristan, Pakistan’s premier hub of Al-Qaeda, Taliban and Afghan insurgents where Islamabad has resisted US pressure for a major ground offensive.

On Sunday, US Defense Secretary Leon Panetta vowed not to let the United States be “gouged” by Pakistan on the price it charges for resuming overland deliveries of American military supplies to Afghanistan.

He also lambasted a tribal court’s decision to sentence government surgeon Afridi to 33 years in prison for helping the CIA track down bin Laden

“What they have done here does not help in the effort to try to reestablish a relationship between the United States and Pakistan,” he said.

The Senate Appropriations Committee has voted to cut US aid to Pakistan by a symbolic $33 million, a sign of growing frustration with Pakistan.