Karachi, Pakistan ? A suicide bomber who was blocked from driving into the U.S. Consulate slammed instead into an American diplomat’s car Thursday, killing the envoy. The force of the blast on the eve of President Bush’s trip to Pakistan blew the U.S. vehicle into the grounds of a hotel.

The attack killed three other people, wounded 52 and shattered windows in the consulate and on all 10 floors of the Marriott Hotel. Ten cars were destroyed, and charred wreckage was flung as far as 600 feet away in one of the most heavily guarded areas of the volatile southern city.

Bush, in neighboring India, quickly vowed to stick with his plan to fly today to Pakistan’s capital, Islamabad.

“Terrorists and killers are not going to prevent me from going to Pakistan,” Bush said. His national security adviser, Stephen Hadley, said there was evidence the U.S. diplomat had been targeted.

Pakistani officials said the bombing could have been timed for Bush’s two-day visit.

“All international media are eyeing Pakistan at this time, and terrorists are using this to defame Pakistan and Muslims,” said Ishratul Ibab, the provincial governor.

No group claimed responsibility for the bombing, which left a crater 8 feet wide and more than 2 feet deep. But Karachi is a hotbed of Islamic militancy, and past attacks have been blamed on al-Qaida-linked militants.

The American was identified by the State Department as David Foy, 52, of Fayetteville, N.C. Foy was married and the father of four daughters. He joined the State Department in 2003 and was assigned to Pakistan last September as a facilities maintenance officer.

The attacker was driving on a road that leads to the consulate but a paramilitary guard signaled him to stop at a checkpoint, said Niaz Sadiqui, the provincial police chief. The bomber then saw the American official’s car and rammed into it 65 feet from the U.S. Consulate’s gate, igniting high-density explosives, Sadiqui said.

“We have reached the conclusion that it was a suicide attack, and we have found body parts of the attacker,” Sadiqui said.

Diplomats’ cars are usually marked by red-colored plates, which could explain why the bomber was able to target the official.

The blast hurled the diplomat’s car across a concrete barrier and into the grounds of the hotel, also killing his Pakistani driver, Iftikhar Ahmed.