WASHINGTON Though the US has yet to investigate the killing of 24 Pakistani soldiers in Nov 26 Nato airstrike, President Obama on Sunday 'revealed to President Zardari that the deadly strike was 'not deliberate attack. Interestingly, President Obama is not the first person to make this claim as Nato/Isaf and US authorities, including Secretary of State Hillary Clinton, have lately shifted their stance to calling the event accidental. The US and officials of western military alliance have been saying previously that the airstrike came in reaction to the firing by Pakistani soldiers. But Pakistan Army has already rejected all such groundless assertions, saying that its preliminary investigation plausibly suggest that it was a wilful pre-mediated attack. The Pakistanis say that Nato bluffed them by deliberately giving them wrong coordinates for the proposed action against militants and that their forces fired only after the attacks began. A White House statement said Obama placed a call early Sunday to Zardari expressing his regrets over the 'tragic loss and promising a 'full investigation into the incident, which has plunged the two uneasy allies into a diplomatic crisis. The statement read: Earlier today President (Barack Obama) placed a phone call to Pakistani President Asif Ali Zardari to personally express his condolences on the tragic loss of twenty-four Pakistani soldiers this past week along the border of Afghanistan and Pakistan. The statement said the US president told his Pakistani counterpart that the attack was accidental in nature and reiterated the United States strong commitment to a full investigation. The US strikes along the border with Afghanistan last weekend set off a wave of anger in Pakistan and further strained Islamabad-Washington ties as the Obama administration tries to wind down the war in Afghanistan. Islamabad has so far refused to take part in a US investigation into the attack. But the White House said Obama and Zardari nonetheless '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 conversation, eight days after the incident, came despite the reservations of some officials in the Defence Department and favoured an approach suggested by diplomats who had urged a more conciliatory gesture. But the presidents comments stopped short of a formal apology or videotaped statement that had been sought by the Pakistani government as a way to ease the intense public anger in that country. Some administration aides had worried that if Mr Obama were to apologise formally to Pakistan, the move could become fodder for his Republican opponents in the presidential campaign. In the wake of the strikes, Pakistan decided not to take part in the Bonn Conference on the future of Afghanistan that opens Monday a decision which, together with the Talibans boycott, has cast the events usefulness into doubt. Pakistan has also shut down Natos vital supply line into Afghanistan and ordered American personnel to leave Shamsi airbase. The base is widely understood to have been a hub for the covert CIA drone war on Taliban and al-Qaeda commanders in Pakistans troubled border areas with Afghanistan. Previous cross-border strikes were investigated jointly and the fallout quickly contained, like the dispute that followed the American helicopter attacks on Pakistani forces in September 2010. But a year of crises that began with an American contractor shooting two Pakistanis to death on a street in Lahore and included the Navy Seal raid northwest of Islamabad that killed Osama bin Laden, now risks ending with the breach of an alliance that has been the cornerstone of American national security policy for the past decade, American officials and analysts have said.