Gunmen kidnapped an American development expert after tricking his guards and breaking into his house in Pakistan on Saturday, a brazen raid that alarmed aid workers, diplomats and other foreigners who already tread carefully in this country rife with Islamic militancy and anti-U.S. sentiment.

U.S. officials identified the man as Warren Weinstein, the Pakistan director for J.E. Austin Associates Inc., an international development consulting company based in Arlington, Va.

"I can confirm that an American citizen working for a private company is missing," said embassy official Alberto Rodriguez. "We are working with the Pakistani authorities."

Police declined to speculate on the motive, and no group immediately claimed responsibility. But kidnappings for ransom are common in Pakistan, with foreigners being occasional targets. Criminal gangs are suspected in most abductions, but Islamic militants are believed to also use the tactic to raise money.

Lahore has seen a number of militant attacks, and the Punjab region where it is located is home to several of Pakistan's top militant networks, some of which are suspected of ties to Pakistani intelligence.

Police said the American, believed to be in his 60s, had returned to his home in the eastern city of Lahore the previous night from the capital, Islamabad. He had told his staff that would be wrapping up his latest project and moving out of Pakistan by Monday, police officer Tajammal Hussain said.

According to Pakistani police, two of the kidnappers showed up at Weinstein's house Saturday and told the guards inside the gate that they wanted to give them food, an act of sharing common during the Muslim holy month of Ramadan, which started early this month.

The guards opened the gate, and five other men appeared. The armed assailants overpowered the guards and stormed into the house. Some gunmen are believed to have entered through the back. They snatched the American from his bedroom, taking nothing else.

A Pakistani friend of Weinstein's said he was advising the provincial livestock department and the Industries Ministry and was working on a development project financed by the U.S. government in the tribal regions, a largely lawless area where militants operate along the border with Afghanistan.

"He was a very experienced man and said he had worked in many countries in difficult circumstances," said the Pakistani acquaintance, who asked not to be identified.

Weinstein, who had been based in Lahore for seven years, tried to assimilate into the local culture and wore the Pakistani national dress, baggy trousers and a long tunic known as a shalwar kameez, and could speak functional Urdu, according to people who know him.