U.S. officials were in intense security talks with officials from several other countries, too, as intelligence concerns about possible plans by the al-Qaida terror network to use aircraft to attack American targets again intensified.

A spokesman for French Prime Minister Jean-Pierre Raffarin said the decision to cancel the six Air France flights came early today after American authorities notified France that "two or three" suspicious people, possibly Tunisian nationals, were planning to board the flights.

A senior U.S. government official, speaking on condition of anonymity, said "people were going to be on the flights that they (French officials) did not want entering the country."

The French Interior Ministry said the flights were canceled at the request of the U.S. Embassy in Paris.

French television station LCI reported that American authorities believed members of al-Qaida may have been planning to board the planes. The Interior Ministry declined to comment on whether any al-Qaida members figured into the incident.

The FBI was taking the potential threats "very seriously," LCI said.

The United States handed French authorities the names of suspicious people who may have intended to board the flights but no people by those names went through airport security checks, the Interior Ministry said, adding that no arrests were made.

Raffarin requested the cancellations based on information "gathered in the framework of French-American cooperation in the fight against terrorism, and which was of a nature that threatened the safety of these flights."

The French apparently had no choice as to whether to allow the flights to take off. A spokesman for Raffarin said the United States had threatened to refuse the planes permission to land.

The U.S. Department of Homeland Security had been meeting with French officials in recent days over concerns about a terrorist attack.

In Washington, one U.S. official who spoke on condition of anonymity said the U.S. government had been trying to keep the negotiations with France confidential, "hoping that we would be able to lure some of these people in."

The official said there was some frustration within the Department of Homeland Security that the flights were canceled, thus allowing the word to get out about the security concerns.

Three of the flights were scheduled to depart today — two from Paris and one from Los Angeles. Air France gave the flight numbers as 68, 69 and 70.