Islamabad: Pulling out of a trilateral meeting with Afghanistan and America scheduled for later this month, Pakistan on Friday summoned the US Ambassador to lodge a strong protest against a drone attack in the country's tribal belt that killed 44 people.

US Ambassador Cameron Munter was summoned by Foreign Secretary Salman Bashir "in pursuance of the directives of Prime Minister Yousuf Raza Gilani" and a "strong protest was made" regarding Thursday’s drone strikes "that caused many casualties," Foreign Office spokesperson Tehmina Janjua said.

Munter was informed that "under the current circumstances, Pakistan would not be able to participate in the trilateral meeting between Afghanistan-Pakistan-US, proposed by the US, in Brussels on March 26," Janjua said.

Minister of State for Foreign Affairs Hina Rabbani Khar was earlier expected to participate in the meeting.

Bashir told the US envoy that such drone strikes were "unacceptable" and constituted "a flagrant violation of humanitarian norms and law."

A strongly worded statement issued by the Foreign Office said Munter was told that it "was evident that the fundamentals of our relations need to be revisited."

"Pakistan should not be taken for granted nor treated as a client state. It was for the White House and the State Department to hold back those who have been trying to veer Pakistan-US relationship away from the track," the statement said.

It quoted Munter as saying that he "understood clearly that this was not a proforma demarche."

He said he would "rush to Washington to convey Pakistan's message to the US administration at the highest levels."

The latest diplomatic row between Pakistan and the US came barely two days after the resolution of a spat over suspected CIA contractor Raymond Davis, who was arrested in Lahore on January 27 after he shot and killed two Pakistani men.

Pakistan's refusal to free Davis on grounds of diplomatic immunity had taken bilateral ties to a new low.

A Pakistani court pardoned and freed Davis on Wednesday after over two million dollars were paid as "blood money" to the families of the two men he had killed.

Just a day after his release, US drones targeted what Pakistani officials said was a tribal jirga in Datta Khel area of the volatile North Waziristan tribal region.

Forty-four people were killed in the attacks, a majority of them members of a tribal council and personnel from a government militia force.

Media reports said some of those killed in the attacks were Taliban militants or had links to the Taliban.

Pakistan had earlier demanded an "apology and explanation" from the US for the drone strikes, which were condemned by President Asif Ali Zardari, Prime Minister Gilani and army chief Ashfaq Parvez Kayani.

Kayani, in a strongly worded statement, said: "It is highly regrettable that a jirga of peaceful citizens, including elders of the area, was carelessly and callously targeted with complete disregard to human life."

(Agencies)