Sept. 21 (Bloomberg) -- The suicide bombing yesterday of Islamabad's Marriott hotel, the city's most prominent American business, may increase tensions between the U.S. and Pakistan over how aggressively to combat terrorism.

The attack, which killed at least 53 and injured 266 near the capital's main government buildings, came hours after President Asif Ali Zardari pledged to resist recent incursions into Pakistani territory by U.S. forces in Afghanistan who are battling Pakistan-based Taliban and al-Qaeda guerrillas.

Zardari made the promise during his first speech to parliament since succeeding Pervez Musharraf on Sept. 9. Zardari's government says it will oppose Islamic insurgents with a combination of negotiation and the selective use of force.

Since 2004, the U.S. has pressed Musharraf, and now his successors, to step up military action against the Taliban and allied groups, which control large swaths of the border zone near Afghanistan. Terrorist assaults killed 2,000 people in Pakistan last year.

``This attack will create more of a disconnect in terms of how the U.S. looks at terrorism in Pakistan and how Pakistan looks at it,'' Hassan Abbas, a former security official and now a researcher on Pakistani politics at Harvard University, said by telephone.

Clashing Views

``The U.S. will see terrorism in Pakistan getting stronger and will think if Pakistan can't control it then they will take control of it. Pakistan will be thinking that U.S. involvement over the past years has led to this reaction,'' Abbas said.

A truck packed with explosives blew up at the Marriott's front gate, creating a 6 meter (20 foot) crater at the main entrance and igniting a fire that gutted the building and continued to smolder today. More than a metric ton (2,200 pounds) of explosive was used in the device, GEO TV reported without saying where it got the information. The detonation was heard 30 kilometers (18 miles) away in the city of Rawalpindi.

The six-story hotel may collapse, according to police officials cited by Dawn News television. Islamabad hospitals and police reported 47 known dead by this morning, a figure that may rise as emergency workers search the building.

The Marriott, which was hit by smaller bombs in 2004 and 2007, is in the city's high-security zone, less than a kilometer from the parliament building, the President's House and the diplomatic enclave.

`Ceiling Collapsed'

``Given the sensitive location of the hotel, the attack shows the complete failure of the Pakistani intelligence and security forces' efforts in the war on terrorism,'' Abbas said.

The hotel's 290 rooms, popular with diplomats, other foreigners and wealthy Pakistanis, weren't heavily booked yesterday, employees said. In the main banquet hall about 300 people, mostly Pakistanis, were eating the ``iftar'' dinner that marks the end of the day's fast during the month of Ramadan.

``The ceiling collapsed, and you couldn't see in the dark,'' said Imtiaz Gul, a journalist who was dining with friends. Survivors groped through clouds of dust to exit through the kitchen, he said.

A Danish diplomat and three U.S. citizens were killed, and Germans and Saudis injured, Dawn News reported, without saying where it got the information. Czech ambassador Ivo Zdarek, who was staying at the hotel, was killed in the attack, said Rehman Malik, senior adviser in the Interior Ministry, who also confirmed the total death toll of 53.

`Cancer of Terrorism'

As rescuers hauled out bodies, a group of armed U.S. embassy employees inspected the Marriott. Wearing civilian clothes and combat helmets, they carried automatic rifles and were unaccompanied by Pakistani police or military officers.

``This incident doesn't deter us from our mission to eliminate the cancer of terrorism from our country,'' Zardari said in nationally televised remarks early today. ``We will save this country.''

Interior Minister Rehman Malik said today that there is ``a possibility of involvement by foreign elements in this attack.'' He said ``sophisticated weapons'' have been smuggled into Pakistan from Afghanistan.

U.S. President George W. Bush, U.K. Foreign Secretary David Miliband and United Nations Secretary-General Ban Ki-moon condemned the attack in separate statements.

``We will fully support the democratically elected government of Pakistan and the Pakistani people as they face enormous challenges economically as well as from terrorism,'' Bush said.

Zardari is scheduled to meet Bush on Sept. 23 in the U.S.

Three-Pronged Strategy

There was no immediate claim of responsibility for the bombing. The last major attack in Islamabad took place on June 2, when a car bomb outside Denmark's embassy killed at least nine people. Al-Qaeda said it was behind that incident.

In his speech to parliament yesterday, Zardari said his government has a three-pronged strategy for terrorism. It includes offering a truce to militants who give up fighting, funding development projects in tribal areas adjacent to Afghanistan to boost their economies and using force only as a last resort against those who attack security forces.

Pakistani forces have killed more than 700 militants in a six-week operation in the tribal area of Bajaur.

Pakistan has accused U.S.-led forces in Afghanistan of carrying out attacks on its territory in the past few months and has demanded an end to such raids, saying they promote militancy as well as violating its sovereignty.

The U.S. views the operations as vital to its efforts to subdue the Taliban insurgency in Afghanistan, saying the Taliban find havens in Pakistan's mountainous tribal regions.

``The challenge for Zardari will lie in balancing his need for domestic political support, which is tenuous, against the demands of those in Washington who want him to move more quickly, within Pakistan, against both the Taliban and al-Qaeda,'' Matt Nelson at London's School of Oriental and African Studies said in an e-mailed note yesterday. ``The new government is trying very hard to carve out an approach to terrorism that can be seen as `Pakistani.'''

To contact the reporters on this story: James Rupert in Islamabad jrupert3@bloomberg.net; Farhan Sharif in Karachi at fsharif2@bloomberg.net.

Last Updated: September 21, 2008 07:18 EDT