(Adds comments from Clinton and adviser Podesta)

By Roberta Rampton

WASHINGTON, July 31 (Reuters) - Republican candidate Donald Trump said he is unhappy with the dates set for this fall's presidential debates, but White House rival Hillary Clinton countered that the schedule was decided long ago and vowed to show up regardless of his objections.

The nonpartisan Commission on Presidential Debates has scheduled three televised debates ahead of the Nov. 8 election - Monday, Sept. 26, Sunday, Oct. 9, and Wednesday, Oct. 19. The dates were set almost a year ago.

Trump and other Republicans said they should be changed because of conflicts with National Football League games.

"I think two of the three are against the NFL, so I'm not thrilled with that," the Republican presidential nominee said in an interview with ABC's "This Week" that aired on Sunday.

Speaking to reporters while campaigning at a cheese barn in Ashland, Ohio, Clinton noted that the debate schedule had been established long before the two major political parties chose their nominees.

"I'm going to be there. That's all I'll say," Clinton said just days after the end of the Democratic National Convention, where the former secretary of state accepted her party's presidential nomination.

In a statement, the commission said the chosen dates "will serve the American public well," adding that it was impossible to avoid all sporting events when working out the schedule. It said the debates had never been rescheduled for such conflicts.

Trump, who tweeted on Friday that Clinton was "trying to rig the debates" so that fewer people would watch, suggested in the ABC interview that his rival wanted the debates to be held "when nobody's home" to watch.

Newt Gingrich, a Trump adviser and former speaker of the U.S. House of Representatives, tweeted that the scheduling "makes me think the commission is rigged to help hide Hillary from the voters."

'MAXIMUM AUDIENCE'

The commission was established in 1987 by the Republicans and Democrats to ensure the debates became a permanent part of the campaign after a series of "hastily arranged" events in 1976, 1980 and 1984 - and no debates in 1964, 1968 and 1972.

Neither party is involved with running the commission, which is governed by an independent board of directors. It is co-chaired by former Republican National Committee chairman Frank Fahrenkopf and Mike McCurry, a former press secretary in Bill Clinton's White House.

David Axelrod, a former senior adviser to President Barack Obama, suggested on Twitter that Trump could be "just trying to ditch" the debates.

When asked directly whether Trump would participate, his campaign manager, Paul Manafort, said the Republican candidate "wants to participate" but also seeks "the maximum audience."

"So we're going to sit down with the commission in the next week or so and we're going to start talking to them and we want to make sure we have a broad audience, understanding, watching the debates," Manafort told CBS's "Face the Nation."

RNC Chairman Reince Preibus said the debates would get more viewers if they were on Tuesday, Wednesday or Thursday nights.

"We're going to be working with the commission and what they're putting together," Preibus said on CBS. "We're not going to agree with anything that our nominee doesn't agree with."

Clinton adviser John Podesta called the complaints "more Trump debate malarkey. We will be at the debates set by the bipartisan debate commission and expect he will too," Podesta said on Twitter.

Trump also told ABC he had received a letter from the NFL saying the debate dates were "ridiculous."

But Brian McCarthy, a spokesman for the NFL, said there was no such letter.

"While we'd obviously wish the debate commission could find another night, we did not send a letter to Mr. Trump," McCarthy said on Twitter.

(Additional reporting by Doina Chiacu and Alana Wise in Washington and Amanda Becker in Ashland, Ohio; Editing by Caren Bohan, Sandra Maler and Paul Simao)

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