PESHAWAR, Pakistan -- A suicide car bomber rammed into a U.S. government vehicle in this northwestern city Monday, killing two Pakistanis and wounding more than a dozen -- including two Americans -- in one of the worst attacks against the United States in Pakistan in recent years, officials said.

The bombing was a vivid reminder of the danger of operating in Pakistan, especially in the northwest, where Taliban and al-Qaida militants are strongest.

The United States has persisted because its work in Pakistan is seen as key to countering militants who threaten American interests in neighboring Afghanistan and elsewhere.

Insurgents have carried out scores of bombings in Peshawar in recent years, but attacks against American targets have been relatively rare because of extensive security measures by the U.S. government -- ones that diplomats sometimes complain limit their effectiveness and ability to move around.

The United States said it would review its security procedures following Monday's attack, which was condemned by Secretary of State Hillary Rodham Clinton.

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"We pray for the safe recovery of both American and Pakistani victims, and once again we deplore the cowardly act of suicide bombing and terrorism that has affected so many around the world," Clinton said in Jakarta, Indonesia, her second stop on a six-nation tour in Asia.

No group has claimed responsibility for the attack in Peshawar, but suspicion will fall on Taliban and al-Qaida militants who have long had their sights set on the United States.