DETROIT, Aug 8 (Reuters) - U.S. Republican presidential

candidate Donald Trump and Democratic opponent Kamala Harris

will debate on Sept. 10 on ABC, setting up the first

face-to-face match-up between the rivals in what polls show is a

close race.

In a news conference at his Palm Beach, Florida, residence,

Trump said he wanted additional debates on Sept. 4 and Sept. 25

that would air on Fox and NBC.

Harris said in a post on X that she was looking forward to

the Sept. 10 debate after Trump "finally committed."

She told reporters after a Detroit-area campaign stop that

she was open to discussing more debates, but a campaign official

reiterated their position that a Sept. 4 Fox debate is off the

table.

Discussions on future debates depend on Trump's

participating in the Sept. 10 debate on ABC, the official said.

The Harris campaign had already opposed a Fox debate, saying the

host network should be one that sponsored recent primary debates

by both parties.

Trump previously suggested he might back out of the ABC

debate, scheduled before Harris, the U.S. vice

president, replaced President Joe Biden as the Democratic

presidential candidate less than three weeks ago, upending the

contest. The Sept. 10 debate on ABC was to be the second of two

agreed upon between Biden and Trump, following their June 27

debate on CNN.

An Ipsos poll published on Thursday found Harris has widened

her lead over Trump since late July. She leads Trump 42% to 37%,

compared with a July 22-23 Reuters/Ipsos survey that showed her

up 37% to 34% over Trump.

Thursday's Palm Beach news conference was Trump's first

public appearance since Harris selected Minnesota Governor Tim

Walz as her running mate on Tuesday.

Harris and Walz have headlined rallies in the battleground

states of Pennsylvania, Michigan and Wisconsin this week,

drawing tens of thousands of attendees in a fresh sign of how

her late entry into the race has galvanized Democrats.

Thursday's stop by the Democratic pair at a union hall came as

the campaign said it sees labor groups as a key to tipping the

balance in the election.

Harris' rapid rise has sent Trump's team scrambling to

recalibrate its strategy and messaging. Opinion polls show

Harris has erased the lead Trump had built over Biden, and

Democrats have raked in hundreds of millions of dollars from

voters and big donors since she became the party's candidate.

Trump insisted on Thursday he has not altered his approach

to the race. In a question-and-answer session with reporters

that stretched beyond an hour, Trump hopped from topic to topic

and said Harris and Walz are weak candidates.

Nevertheless, Trump lamented that he isn't able to face

Biden in the Nov. 5 election, suggesting the president was a

victim of a plot to dislodge him from atop the Democratic

ticket.

Biden dropped his faltering reelection bid under pressure

from fellow Democrats worried about his chances of victory after

a poor debate performance against Trump.

Asked about his controversial comments last week that

Harris, who is of Black and Indian decent, recently "happened to

turn Black," Trump said: "You'll have to ask her that question,

because she's the one that said it, I didn't say it. ... To me

it doesn't matter. But to her, from her standpoint, I think it's

very disrespectful to both, really, whether it's Indian or

Black, I think it's very disrespectful to both."

Trump's initial comments, delivered to an audience of

Black journalists, drew widespread condemnation and left donors

and aides baffled and alarmed. The Trump campaign didn't

immediately comment further to provide evidence of remarks by

Harris that Trump said he was referring to.

Trump on Thursday also mocked the size of Harris' campaign

crowds, even though they have matched his of late. He falsely

claimed the size of the crowd he addressed on Jan. 6, 2021 - the

day his supporters stormed the U.S. Capitol - was as large as

those who packed the National Mall in Washington for Dr. Martin

Luther King Jr.'s "I Have a Dream" speech in 1963.

"We actually had more people," Trump said. "But I'm ok with

it, because I liked Dr. Martin Luther King."

King delivered his speech to an estimated 250,000 people in

August 1963, according to the National Constitution Center.

Trump's rally on Jan. 6, 2021, drew about 53,000 supporters,

according to the House of Representatives Select Committee's

"187 minutes of dereliction" report.

Echoing a recent attack line from his campaign, Trump

criticized Harris for not doing a press interview since

launching her campaign.

"She can't do an interview. She's barely competent," Trump

said, later again calling her "nasty," a go-to line that he

often uses to disparage female critics.

Trump has conducted a steady stream of media interviews,

though they are usually with friendly, right-leaning outlets and

reporters. On Wednesday, he called into the "Fox & Friends"

morning program and took questions from the program's hosts.

Trump announced the Palm Beach news conference on Thursday

morning on his social media platform. Only a select group of

reporters were given the advance notice needed to travel to his

Florida resort in time. Reuters was not extended an invitation.

Harris answered a handful of questions from reporters after

meeting with auto workers in Wayne, Michigan, on Thursday,

following the United Auto Workers union's endorsement of her

candidacy. She said she wants to schedule a sit-down interview

"before the end of the month."