The United States closed its consulate in this southern Pakistani city on Tuesday due to a security threat.
The consulate in Karachi warned American citizens not to visit the building or the nearby Marriott Hotel until further notice.
“We received information that increased our security concerns,” U.S. Embassy spokesman Greg Crouch said from the capital, Islamabad.
He declined to discuss the nature of the threat but said the consulate would reopen Wednesday.
Karachi is Pakistan’s largest city and a hotbed of Islamic militancy. Militants have launched a string of attacks, including two against the U.S. Consulate, in recent years.
In June 2002, a suicide bombing near the U.S. Consulate left 14 Pakistanis dead and in March last year police defused a huge bomb less than five minutes before it was timed to detonate outside the building.
Islamic militants have been angered by the U.S.-led war against that ousted the Taliban militia from power in neighboring Afghanistan in late 2001 for harboring al-Qaida.
They are also opposed to President Gen. Pervez Musharraf’s alliance with Washington in the anti-terrorism campaign.