Last month, the White House appointed a senior DP World executive, David C. Sanborn of Virginia, to be the new administrator of the Maritime Administration of the Transportation Department. Sanborn worked as DP World's director of operations for Europe and Latin America.

Critics of the proposed purchase said a port operator complicit in smuggling or terrorism could manipulate manifests and other records to frustrate Homeland Security's already limited scrutiny of shipping containers and slip contraband past U.S. Customs inspectors.

"When you have a foreign government involved, you are injecting foreign national interests," Kreitzer said. "A country that may be a friend of ours today may not be on the same side tomorrow. You don't know in advance what the politics of that country will be in the future."

Shipping experts noted that many of the world's largest port companies are not based in the U.S., and they pointed to DP World's strong economic interest in operating ports securely and efficiently.

"Does this pose a national security risk? I think that's pushing the envelope," said Stephen E. Flynn, who studies maritime security at the New York-based Council on Foreign Relations. "It's not impossible to imagine one could develop an internal conspiracy, but I'd have to assign it a very low probability."

Changing management over the U.S. ports "doesn't offer al-Qaida any opportunities it doesn't have now," said James Lewis, who worked with the U.S. committee at the State and Commerce departments. "It's in Dubai's interest to make sure this runs well. There is strong economic incentive to be sure these worries never materialize."

Flynn and others said even under foreign control, U.S. ports will continue to be run by unionized American employees. "You're not going have a bunch of UAE citizens working the docks," Flynn said. "They're longshoremen, vested in high-paying jobs. Most of them are Archie Bunker-kind of Americans."

Peninsular and Oriental and DP World set approval by the U.S. security committee as a condition for the sale. In regulatory papers, the companies said either the committee must agree not to formally investigate the purchase or Bush must not move to block the sale for national security purposes.

Since the Sept. 11 attacks, the FBI has said the money for the strikes was transferred to the hijackers primarily through the UAE's banking system, and much of the operational planning for the attacks took place inside the UAE.

Many of the hijackers traveled to the U.S. through the UAE. Also, the hijacker who steered United Airlines flight into the World Trade Center's south tower, Marwan al-Shehhi, was born in the UAE.

After the attacks, U.S. Treasury Department officials complained about a lack of cooperation by the UAE and other Arab countries trying to track Osama bin Laden's bank accounts.