NEW YORK (AP) _ Jay Leno keeps making wisecracks about Amtrak, but Amtrak isn't laughing.

After months of complaints to NBC about being the butt of Leno's humor on ''The Tonight Show,'' the passenger railroad has trained its ire on NBC's bottom line by canceling about $2 million in advertising.

''Our advertising couldn't keep up with their jokes,'' Amtrak spokesman Howard Robertson said today.

He said for more than a year individual Amtrak employees had written to NBC on their own initiative and encouraged the railroad to take action.

Finally last week, Amtrak advised the network it was yanking its ads.

''They said they were hopeful we would reconsider,'' Robertson said.

NBC had no immediate comment. Leno could not be reached for comment.

Leno jokes have focused on Amtrak's safety. A typical jab, as quoted in The Washington Post today, had the talk show host commenting on Amtrak's announcement that it would lay off 600 managers. Leno cracked that the company didn't plan to fire the workers, just put them on one of its trains.

''Any major corporation is going to have jokes made about them, and we understand that,'' Robertson said. ''But even though recent (Amtrak) accidents haven't been our fault, the jokes have been more frequent and less tasteful.''

Leno isn't alone to poke at Amtrak. CBS rival David Letterman has been razzing Amtrak on his ''Late Show,'' but Robertson said no action has been taken against CBS.

At least, not yet. Letterman, he said, ''made a joke about Amtrak earlier this week. We'll take a look at that as well.''