BERLIN (AP) _ A German travel company said Friday it will see to the return of about 4,000 German tourists stranded in the United States, and a tourism official demanded action against the U.S. charter airline that canceled their flights home.

American Trans Air of Indianapolis, canceled on Wednesday all flights booked through Hamburg tour operator Marlo Reisen, complaining of unpaid bills.

The league of German travel agencies and the Fun Tours company said they would organize flights for German tourists stranded in Florida and California.

Last month, about 10,000 German tourists were stuck in the United States and other vacation spots after MP Travel Line, a German charter company, filed for bankruptcy.

Otto Schneider, head of the league, said Marlo Riesen lost half its customers when MP Travel folded and should have shut down its business immediately instead of continuing to send tourists abroad.

Schneider also told The Associated Press he wrote the Transport Ministry suggesting action against American Trans Air. He cited German legal precedents requiring carriers to honor return tickets even if a travel agency has not paid for them.

But American Trans Air said earlier in a news release, ''The laws governing foreign-originating air charter operations in the U.S. and in Germany indicate that the responsibility for customers left without transportation is clearly that of the tour operator.''

Fun Tours spokeswoman Susanne Apfelstaedt said the travelers would be flown home without having to buy new tickets, though the travel agencies would later have to work out who will pay.

Mary Cochran, spokeswoman for American Trans Air, said in Indianapolis on Wednesday that the charter flew 19 flights that went unpaid before discontinuing the others. She said American Trans Air notified Marlo Reisen Tuesday it was canceling the remaining flights.

''It just reached a point that it became obvious that they were not going to pay us, and we were not going to be able to absorb the cost of the flights,'' Cochran said.