US Secretary of State Hillary Clinton on Saturday called Pakistan's prime minister to offer condolences over the deaths of 24 Pakistani troops killed in NATO air strikes, the State Department said.

In the call with Yousuf Raza Gilani, Clinton "reiterated America's respect for Pakistan's sovereignty and commitment to working together in pursuit of shared objectives on the basis of mutual interest and mutual respect," it said.

"She once again expressed condolences to the families of the soldiers and to the Pakistani people for the tragic and unintended loss of life," it said in a statement.

Following the strikes, Pakistan decided not to take part in this week's Bonn conference on the future of Afghanistan -- a decision which, together with the Taliban's boycott, has cast the event's usefulness into doubt.

A statement from Gilani's office said he told Clinton that Pakistan's non-attendance was not open to review since it had already received the backing of parliament's national security committee.

The committee "has supported the decision of the cabinet not to participate in the Bonn Conference," the statement quoted Gilani as telling Clinton.

Meanwhile, he said, parliament was looking into the general issue of Pakistan's relationship with the United States.

"The parliament was seized of the matter of terms of cooperation with the US. This will ensure national ownership and clarity about the relationship," the statement quoted him as saying.

Islamabad has so far refused to take part in a US investigation into the air strikes on the Afghan border which killed 24 Pakistani soldiers on November 26.

The incident has exacerbated fears of a prolonged crisis in relations, after Pakistan also shut down NATO's vital supply line into Afghanistan and ordered American personnel to leave Shamsi air base.

The base is widely understood to have been a hub for the covert CIA drone war on Taliban and Al-Qaeda commanders in Pakistan's troubled border areas with Afghanistan.