WASHINGTON — Passengers abroad soon will be checked against lists of suspected terrorists before their planes take off for American cities, the Homeland Security Department said yesterday.

The new rule, to go into effect by the end of the year, aims to allow U.S. authorities more time to check passengers' information against the FBI's comprehensive terrorist watch lists, according to Homeland Security Deputy Secretary Michael Jackson.

It also could halt the practice of diverting or sending back planes once they're in the air because current rules don't give authorities enough time to check if a passenger is on a watch list before a plane departs.

"It's a lot easier to take one person off a plane and sort it out (abroad) than inconvenience a whole planeload of people," Jackson said.

Passengers' names are now checked abroad by airlines against a "no-fly list" that is not as complete as government watch lists.

After takeoff, the airlines send the passenger information to government agents to be checked against the watch lists. That leaves agents racing the clock to determine whether a passenger with the same or a similar name to someone on a watch list is really a threat.

The new rule would allow the government to finish checks against the watch lists at least 15 minutes before the plane leaves the gate at a foreign airport, Jackson said.

That could buy agents enough time to avoid rerouting an international flight where a passenger's name mistakenly appears on a watch list. In May 2005, for instance, two trans-Atlantic flights were diverted to Bangor, Maine, in the same week after passengers with names similar to terrorists were flagged while the flights were en route to America.

And in 2004, a London-to-Washington flight was diverted after passenger Yusuf Islam, the singer once known as Cat Stevens, appeared on the no-fly list.

Nathalie Herbelles of the Association of European Airlines said Homeland Security's 15-minute requirement is an improvement over an earlier proposal that would have required airlines to send passenger information 60 minutes before takeoff. That, she said, would have caused chaos at airports worldwide because passenger lists aren't ready that far in advance.