NEW YORK -- Veteran journalist Mark Halperin is apologizing for what he terms "inappropriate" behavior after five women claimed he sexually harassed them while he was political director of ABC News.

The co-author of the best-selling book "Game Change" told CNN Wednesday night that he's "deeply sorry" and is taking a "step back" from day-to-day work as an analyst for NBC News to deal with the situation.

Later, NBC News said in a statement to CNN that Halperin is "leaving his role" at NBC News until "questions around his past conduct are fully understood."

Get Breaking News Delivered to Your Inbox

"We find the story and the allegations very troubling," NBC News said.

Two other companies announced they were cancelling book and movie deals.

In his statement to CNN Wednesday night, Halperin said, "During this period, I did pursue relationships with women that I worked with, including some junior to me. I now understand from these accounts that my behavior was inappropriate and caused others pain."

His statement came after CNN reported allegations that Halperin, 52, propositioned, fondled and pushed himself against five women in the early 2000s while he was ABC News' political director.

The women, who asked to remain anonymous, said they didn't report Halperin's conduct because they feared retribution or were embarrassed.

Halperin says he pursued relationships, sometimes with junior co-workers, but CNN says he denies the groping allegations.

After the initial report by CNN, several more women came forward in the Washington Post with similar accounts.

Halperin had been signed to co-author a book with John Heilemann on the 2016 campaign, but the publisher Penguin Press said that "in light of the recent news" it has decided to cancel those plans.

HBO, which like CNN is owned by Time-Warner, released a statement saying it would no longer move forward with plans for a miniseries based on the book. "HBO has no tolerance for sexual harassment within the company or its productions," it said.

Showtime, which featured Halperin in the series "The Circus: Inside The Greatest Political Show on Earth," issued a statement suggesting the show's future was uncertain.

"During Mark's time working with us, we have not seen nor have there been allegations of any untoward behavior. We are aware of these reports and will continue to evaluate all options should we decide to move forward with another season of THE CIRCUS. There is no tolerance for sexual harassment within SHOWTIME and its productions," the channel said.