KARACHI — A suicide bomber yesterday rammed a car packed with explosives into a vehicle carrying an American diplomat in Karachi. At least four people, including the diplomat, were killed and 52 injured outside the US Consulate. The American was identified by Pakistan officials as David Foy.

The attack came less than two days before President George W. Bush is scheduled to make a trip to Pakistan, a key ally in the US-led “war on terror,” although he is due to go to the capital Islamabad and not Karachi.

“I have been briefed on the bombings and we have lost at least one US citizen in the bombing — a foreign service officer,” Bush said in New Delhi, where he is on the second leg of a South Asian tour that has also taken him to Afghanistan.

“Terrorists and killers are not going to prevent me from going to Pakistan,” he added.

The blast ripped through a roadside parking lot of the Marriott Hotel, about 20 meters from the consulate gate, shattering windows at the consulate and on all 10 floors of the hotel. Ten cars were destroyed, and charred wreckage was flung as far as 200 meters.

Pakistani police said preliminary inquiries indicated that it was a suicide attack. “The evidences we have collected show that it was a suicide attack,” Karachi police chief Niaz Siddiqui told a news conference.

Investigators said they believed the bomber was a man in his early 20s who parked behind the Marriott about 30 minutes before the attack, walked into the hotel, then returned to sit in the car. “As soon as the diplomatic vehicle entered the lane, he switched on the ignition and reversed the car at high speed into the US vehicle,” a senior investigator said.

Siddiqui said the attacker wanted to hit the US Consulate, but a Pakistani paramilitary guard saw him and tried to stop him, so the attacker drove his car into the diplomat’s vehicle instead. The guard was also killed in the blast.

The diplomat’s car was blown into the air, across a concrete barrier and into the grounds of the hotel, and the driver, a Pakistani working for the consulate, also died. The other fatality was an unidentified woman. One male body, with part of its head missing, was flung by the blast onto the second story of the hotel’s exterior.

Witnesses said the powerful blast triggered a second, smaller blast, possibly of a burning car. A witness, who was going to his office at the ABN-Amro bank building, told Arab News he was forced to stop his car after the car’s windshield was shattered by the explosion and debris fell on his car bonnet. He saw terrified and bleeding people fleeing the smoke-filled area.

President Gen. Pervez Musharraf offered his condolences to Bush over the death of the diplomat. He strongly condemned the blast.

“We condemn this outrage in the strongest terms. Our authorities are investigating the incident and those responsible will be brought to justice,” he wrote in a message to Bush, who is due to arrive in Pakistan late on Friday.

“The Pakistani nation offers its deepest sorrow and sympathy to the government and people of the United States,” he said.

The Pakistani leader, a key US ally in the US-led fight against terrorism, said that “this senseless act will not deter our strong resolve to pursue the relentless fight against the evil of terrorism.”

In a separate message to Bush, Pakistani Prime Minister Shaukat Aziz said the attack was “aimed not only at the Pakistani nation but also our friendly ties with the United States.”