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 to Pakistan's capital, Islamabad, on Friday.

"Terrorists and killers are not going to prevent me from going to Pakistan," Bush told reporters. 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 eight feet wide and more than two feet deep. But Karachi is a hotbed of Islamic militancy, and past attacks have been blamed on Al Qaeda-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. Falak Khurshid, a deputy inspector-general of police in Karachi, said the plates allow diplomats to avoid routine checks although they can choose not to have them for security reasons. It wasn't clear if Foy's wrecked car had such plates.

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. The others who died in the blast were the paramilitary guard and an unidentified woman.

The 52 wounded people included a young Moroccan girl hit by debris, according to provincial government spokesman Salahuddin Haider. He said investigators were trying to obtain video footage from surveillance cameras at the consulate.

There have been other attacks on or near the U.S. Consulate, located in an upscale district of Karachi's sprawling downtown. A car bombing killed 14 people in June 2002. Eight months later, two police guards outside the consulate were shot in an armed assault. In March 2004, police defused a huge bomb in a van minutes before it was timed to explode outside the mission's walls.

The last U.S. Embassy employee to be killed in an attack in Pakistan was Barbara Green, who died with her 17-year-old daughter when a grenade was tossed into a church in March 2002 in Islamabad.

Protesters were already out in full force Thursday before Bush's arrival. Scores of demonstrators chanted "Death to Bush!" and other anti-U.S. slogans in streets in several Pakistani cities.

When Bush arrives Friday night, security was expected to be extraordinarily tight in Islamabad, about 1,000 miles north of Karachi. Thousands of troops and police were to be deployed in the capital, and commandos were to guard the route of Bush's motorcade, officials said.

"We don't think the Karachi blast will have any negative impact on the American president's visit," said Sheikh Rashid Ahmed, the chief government spokesman. "Absolutely, he will be safe here."

When President Bill Clinton visited Islamabad six years ago, residents were told to stay indoors and streets were eerily empty. Before flying here from India, Clinton switched planes at the last minute and arrived in an unmarked white aircraft, just after a USA-marked decoy jet landed.

Securing Islamabad should be easier than policing Karachi. Islamabad is a sleepy, orderly capital that has been carefully planned out. Karachi is a crowded and chaotic metropolis and is Pakistan's biggest city.

The State Department and the American Foreign Service Association mourned Foy's death.

"We will do all that we can, working with the Pakistani government, to see that those responsible for the attack face justice for what they have done," department spokesman Sean McCormack said.

"This tragic loss underlines the mortal dangers faced by the men and women of the U.S. foreign service who are working under the most extreme circumstances to advance our nation's vital interests around the world," association president J. Anthony Holmes said.