The two-decade-old news program was threatened by ABC's strong bid for Letterman. His talk show would have supplanted "Nightline" in the 11:35 p.m. time slot, but Letterman chose to stay at CBS.
Stung by the prospect that he would lose his time slot, Koppel publicly called for a clear signal from ABC parent Walt Disney Co. that "Nightline" could count on serious corporate backing. He said the show deserved "more than bland assurances or a short-term guarantee."
Disney President Robert Iger issued a statement Monday promising to "renew and reaffirm our support for `Nightline,' one of the network's signature programs."
A month of private talks produced an agreement in which Koppel said Monday that "it's possible to say `Nightline' is even stronger than it was before."
Statements issued by Disney and ABC mentioned no specific promises. But a person with knowledge of the talks who spoke on the condition of anonymity said "Nightline" had been promised its time slot for at least two years.
"It took some time to work everything out, but I'm very pleased with how it's come out in the end," Koppel said.
Iger said: "We look forward to working with ABC News to make a strong program even stronger in the coming years. We are confident that `Nightline' will continue to set a high standard for television journalism for years to come."
ABC is unlikely to have given up its hope for a more profitable late-night entertainment show, but no surefire talent appears on the horizon.
ABC News President David Westin said he did not believe "Nightline" had suffered permanent damage from the episode.
"Normally things like this would be dealt with entirely internally," Westin said. "But because there had been so much reporting and speculation, I think that everyone concluded and, more importantly, Bob concluded, that we put it all to rest."
Westin also said he was comfortable with his support from ABC management. The network's chief news executive found out about ABC's courtship of Letterman only hours before it was made public, and several weeks after it was going on privately.
Westin said he believed Koppel had been unfairly criticized by stories that talked about his contractual agreement to anchor the show three nights a week.
He wouldn't talk about any changes planned for the show.
Koppel said he didn't believe any changes were needed.
"I don't want to leave the impression that we're complacent about the broadcast in any way," he said. "We have been working as hard as we can to keep 'Nightline' fresh, to keep it on the news, to keep it as relevant as we can possibly make it."