US presidential candidates Donald Trump and Kamala Harris will meet for their first face-to-face match up within weeks – after Trump said he had agreed to two more debates.

In a rambling news conference at his Mar-a-Lago home in Florida on Thursday (US time) – his first in months – Trump said he had agreed to a debate on September 10, and wanted two more on September 4 and September 25 that would air on Fox and NBC.

Harris said on X that she was looking forward to the September 10 debate on America’s ABC after Trump “finally committed”. After a campaign stop in Detroit, she said she also was open to discussing more debates.

“I’m glad that he’s finally agreed to a debate on September 10th. I’m looking forward to it, and I hope he shows up,” she said.

Trump had previously suggested he might back out of the ABC debate, which was scheduled before Harris replaced President Joe Biden as the Democratic presidential candidate less than three weeks ago, upending the contest.

An Ipsos poll published on Thursday found Harris had widened her lead over Trump since late July. She leads Trump 42 per cent to 37, compared to a July 22-23 Reuters/Ipsos survey, which showed her up 37 per cent to 34 over Trump.

Thursday’s news conference was Trump’s first public appearance since Harris revealed 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 galvanised Democrats.

Her rapid rise has sent Trump’s team scrambling to recalibrate their 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 in a matter of weeks.

Trump insisted on Thursday he had not altered his approach to the race, arguing that Harris shared responsibility for Biden’s record.

In a question-and-answer session last lasted more than an hour, Trump hopped from topic to topic, claiming Harris and Walz were weak candidates who were already dropping in the polls.

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.”

He 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 January 6, 2021 – the day his supporters stormed the US Capitol – was as large as the one that packed the National Mall in Washington for Dr Martin Luther King’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.”

Echoing a recent attack line from his campaign, Trump criticised 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 he often uses to disparage female critics.

He also responded to Biden’s suggestion – in an interview to air in the US on Sunday – that there might be no peaceful transfer of power if Trump loses November’s presidential election.

“Of course there will be a peaceful transfer,” Trump said.

“I just hope we have honest elections.”

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.

– AAP