WASHINGTON, Dec 4: US President Barack Obama on Sunday telephoned President Asif Ali Zardari and assured him that last week’s Nato strikes at military posts in Mohmand were not a deliberate attack on Pakistan.

Earlier, the White House rejected claims that President Zardari and the former Pakistani ambassador to the United States, Husain Haqqani, had advance knowledge of the May 2 US raid on Osama bin Laden’s compound in Abbottabad.

President Obama’s call to Mr Zardari came a day after his Secretary of State Hillary Clinton telephoned Prime Minister Yousuf Raza Gilani and urged him to reconsider Pakistan’s decision to boycott an international conference on Afghanistan which begins in Bonn, Germany, on Monday. Mr Gilani politely turned down her request.

Both Mr Obama and Mrs Clinton offered condolences over the death of 24 Pakistani soldiers in Nato air strikes but it’s not clear if, like his secretary of state, the US president also urged Mr Zardari to send a delegation to Bonn.

“Earlier today the president placed a phone call to Pakistani President Asif Ali Zardari to personally express his condolences on the tragic loss of 24 Pakistani soldiers this past week along the border of Afghanistan and Pakistan,” said a White House statement issued after the call.

“The president made it clear that this regrettable incident was not a deliberate attack on Pakistan and reiterated the United States’ strong commitment to a full investigation,” the White House said.

“The two presidents reaffirmed their commitment to the US-Pakistan bilateral relationship, which is critical to the security of both nations, and they agreed to stay in close touch,” the statement said.

Later, a think-tank expert told CNN that Pakistan should not expect an apology from Mr Obama at this stage as it would hurt his re-election bid.

On Saturday afternoon, the White House took the unusual step of denying a press report which did not have any attribution to the US president’s office. Usually, the White House ignores such reports.

But this time, the White House not only noticed a Pakistani-American businessman Mansoor Ijaz’s article in the Newsweek but also issued a terse statement, rejecting his claim that President Zardari and Mr Haqqani knew about the May 2 raid but decided not to share it with the Pakistani military.

“There is no truth to the reports that Ambassador Haqqani or President Zardari had advance knowledge of the May 2 Abbottabad operation,” said the White House statement. “As we’ve said repeatedly, given the sensitivity of the operation, to protect our operators we did not inform the Pakistani government, or any other government, in advance.”

Diplomatic circles in Washington say the allegation, if proven, could undo the current civilian set-up in Pakistan and that’s why the White House felt the need to publicly deny Mr Ijaz’s claim.

Mr Ijaz’s earlier claim that Mr Haqqani dictated to him a memo seeking US support to rein in the Pakistani military forced the ambassador to resign and has already strained relations between the civilian and military establishments in Pakistan.

But the Nov 26 Nato strikes are having even a greater, and obviously negative, impact on US-Pakistan ties. Pakistan not only opted out of the Bonn conference but has also refused to take part in a US investigation into the incident.

Commenting on media reports that Pakistan Army Chief Gen Ashfaq Parvez Kayani had issued direction that his commanders on the Af-Pak border can return fire without permission, Pentagon spokesman Navy Capt John Kirby said: “Every sovereign nation has the right of self-defence and the right to order their troops to defend themselves. That’s what my understanding is what he did: He reiterated their right of self-defence. We certainly respect that right of his. We have it as well.”