Peshawar, Pakistan (CNSNews.com) - A suicide bomber blew himself up at a checkpoint in northwest Pakistan on Tuesday, killing five people in one of the deadliest terrorist attacks since Taliban leaders suspended talks with the government.

One of those killed in the blast in Bannu was a policeman, district police spokesman Dar Ali Khattak said.

Seven people were injured, including four policeman and a soldier, he said. "We are investigating the matter and at this point cannot say who is responsible for the attack."

Bannu houses a Pakistan military garrison from where operations have been carried out against militant factions in adjoining tribal areas, which have long remained outside effective government control.

Over recent months, various militant organizations have regrouped, with some forming Tehrik-e-Taliban Pakistan (Pakistan Taliban Movement), establishing a strong support basis in the tribal areas and in parts of the neighboring North West Frontier Province (NWFP), both of which border Afghanistan.

Pakistan's newly elected Prime Minister Yousaf Raza Gilani pledged to "redefine" the war on terror and to restore peace by engaging the Taliban in talks and development initiatives.

The shift of strategy saw Tehrik-e-Taliban militants declare a unilateral truce last month. The government also reached an agreement with jailed militant Maulana Sufi Muhammad, who committed himself to shunning violence in return for release after six years' imprisonment.

(In 2001, Muhammad, who heads the Movement for the Enforcement of Mohammedan Law, led 10,000 men fighting against the forces of the pro-U.S. Northern Alliance in Afghanistan. Muhammad is also the father-in-law of a leading pro-Taliban cleric, Maulana Fazlullah, who has been a key target of security force operations since last September. Fazlullah, who uses an unlicensed radio station to spread a hard-line message including opposition to education for girls, continues to elude the troops and has strengthened his position in the upper mountainous areas of the conflict-ridden district.)

Islamabad's much touted peace process appears to have failed, however, following a deadlock over Taliban demands for the withdrawal of more than 80,000 security forces from the tribal belt.

Moulvi Omar, a Taliban spokesman, told reporters in Peshawar, the NWFP capital, that after the failure of the peace talks Taliban fighters were not bound to observe the ceasefire and were free to attack government installations and security personnel.

Official sources say talks are continuing through various channels, however.

The Bush administration has long viewed Pakistan government deals with the militants with suspicion. Deputy Secretary of State John Negroponte on Tuesday said the U.S. expected the civilian and military leadership in Pakistan to be "strong partners against violent extremists" in the frontier region.

Americans "don't want to see the tribal area being used as a platform for plotting and executing international terrorist activity against the West," he said at the Washington-based National Endowment Fund for Democracy.

"So any kind of agreement or understanding which might be negotiated, we would have to look at in the light of those imperatives for United States policies," Negroponte added.

Experts in Pakistan believe that if the Taliban insurgency in the tribal areas is not checked it will expand into other parts of the country. The involvement of foreign jihadists has added to the difficulties faced by the government, and the U.S. is concerned that the Taliban-allied al-Qaeda terror network is rebuilding its strength in the NWFP and tribal areas..

Syed Irfan Ashraf, a Peshawar-based political analyst, says different Taliban commanders have marked off various parts of the tribal belt for themselves, adding that government authority in the area "has ceased to exist."

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