United Airlines and Amtrak yesterday announced combination air and train travel packages, similar to the air and cruise ship packages that have been popular for years.

Starting Jan. 2, passengers can fly cross-country and return by train, or they can fly to certain specified cities and take regional train tours, returning to the gateway city to fly home.

The marketing gambit is aimed at leisure travelers who might be tempted to take a long train trip but don't have enough time, according to Amtrak. A cross-country train trip takes at least four days, according to spokeswoman Patricia Kelly.

"Long-distance train trips have enormous appeal among prospective Amtrak passengers, but many people lack the vacation time for a cross-country train trip both ways," said Timothy P. Gardner, Amtrak's vice president of passenger marketing.

In the past, Amtrak said, some passengers bought expensive one-way fares -- one for airline travel and the other for train travel -- to make the same trip.

The transcontinental fare during the summer and holiday peak-travel periods will be $499. Off-season, the combination will cost $419. In contrast, Amtrak's popular "All Aboard, America" fare, which allows 45 days of travel with stops at any destination, costs $339. The regional packages range from $349 to $489 peak and from $299 to $419 off-peak.

The new Air-Rail Travel Plan is coach class and may be combined in a package with other features, including lodging and sightseeing.

The gateway cities for travelers whose trips begin on the East Coast are Minneapolis-St. Paul, Omaha, Kansas City, Mo., Dallas- Fort Worth and Houston. For instance, a traveler could fly to Minneapolis, take Amtrak's Empire Builder across the Northwest to Seattle and back, and then fly home.