US 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 residence in Palm Beach, Florida, Trump said he wanted additional debates on Sept. 4 and Sept. 25.

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 (DIS.N), opens new tab 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.