But the French interior ministry said on Wednesday it was too soon to draw any conclusions about the man's identity or his suspected ties to al-Qaida.

"I can confirm to you that we are looking for someone. I can't tell you any more than that," French Justice Minister Dominique Perben said.

Government spokesman Jean-Francois Cope later added the suspect had been booked on one of the US-bound Air France flights grounded over the Christmas holidays.

US television network ABC reported on Tuesday that a search had been launched for the man, who US law enforcement officials believe is an Afghan national.

"I can confirm to you that we are looking for someone. I can't tell you any more than that"

Dominique Perben,
French Justice Minister 

Cancelled flights 

International concern about the man, who was reportedly travelling with a French passport, was one of the factors contributing to security jitters about transatlantic flights.

A global air security alert has forced the cancellation of several flights over the past two weeks, including six Air France flights linking Paris and Los Angeles on 24 and 25 December. 

The United States raised its nationwide terror alert on 21 December, warning that al-Qaida was planning an even bigger attack than the September 11 strikes.

Sources close to the investigation in Paris said the suspect bore a name with a phonetic resemblance to that of a man captured by US forces in Afghanistan but who managed to escape.

The US authorities noted the similarity in the two names and alerted their French counterparts, but the man's date and place of birth were not known, the sources said, making a definitive identification difficult.

Small bomb?

ABC reported that French officials feared the suspect may have a small bomb that could get past airport security devices, but sources in Paris were unable to confirm that report.

French Interior Minister Nicolas Sarkozy said only that it was "too soon to make any statements" about the matter.

"I prefer to speak about it once all information has been verified," he said.

Later, an interior ministry source said French investigators had uncovered "no new information to confirm the theory advanced by the American media".

"When a friendly nation asks us to step up security on our side, no one can reproach it for that. I much prefer to act too soon rather than too late"

Nicolas Sarkozy,
French interior minister

Following the grounding of the Air France flights, a thorough search by French investigators turned up nothing suspicious, and officials later said several passengers had been wrongly flagged as potential "terrorists".

Heightened concern

Air France resumed its flights between Paris and Los Angeles on 26 December.

Amid heightened international concern over air security, Washington issued an emergency directive last week asking that armed sky marshals be placed on all foreign flights thought to be at risk.

France backed the US request, with Sarkozy saying on Friday: "When a friendly nation asks us to step up security on our side, no one can reproach it for that.

"I much prefer to act too soon rather than too late."