Donald Trump has challenged Joe Biden to another TV debate and a round of golf, calling it a chance for Biden to “redeem himself” amid the fallout from his disastrous performance last month.

“I’m officially offering Joe the chance to redeem himself in front of the entire world,” Trump said at a rally in Florida on Tuesday (US time).

“Let’s do another debate this week so that sleepy Joe Biden can prove to everyone all over the world that he has what it takes to be president. But this time it will be man-to-man, no moderators, no holds barred. Just name the place, anytime, anywhere.”

Trump, the Republican challenger for the US presidency, then went on

“I’m also officially challenging crooked Joe to an 18-hole golf match right here on Doral’s Blue Monster, considered one of the greatest tournament golf courses anywhere in the world, one of the great courses of the world,” he said.

“It will be among the most-watched sporting events in history. Maybe bigger than the Ryder Cup or even the Masters.

Trump said he’d “even give Joe Biden 10 strokes a side”.

“That means 20 strokes, in case you don’t play golf,” he told his cheering supporters.

“If he wins, I will give the charity of his choice, any charity of his choice, $1 million. And I’ll bet you he doesn’t take the offer.”

The debate offer is unlikely to be taken up, if only because Biden is in Washington DC this week, attending the NATO summit with other world leaders. On Friday, he heads to Detroit to campaign.

He and Trump are scheduled to hold a second debate in September.

After Trump’s challenge, Biden spokesperson James Singer hit back.

“We’d challenge Donald Trump to create jobs, but he lost three million. We’d challenge Donald Trump to stand up to [Vladimir] Putin, but he bent the knee to him. We’d challenge Donald Trump to follow the law, but he breaks it. We’d challenge Donald Trump to not destroy our country,” he said.

“Joe Biden doesn’t have time for Donald Trump’s weird antics – he’s busy leading America and defending the free world. Donald Trump is a liar, a convict, and a fraud only out for himself – par for the course.”

Elsewhere, The Washington Post reported in an investigation in 2016 that Trump’s promised charity donations often failed to materialise.

Biden, 81, has endured 12 days of withering questions about his fitness for office as some of his fellow Democrats on Capitol Hill and campaign donors fear that he will lose the November 5 election after his halting debate performance on June 27.

On Tuesday at the NATO summit, he pledged to forcefully defend Ukraine against Russia’s invasion, using the global stage to show allies at home and abroad that he can still lead.

“Putin wants nothing less, nothing less, than Ukraine’s total subjugation … and to wipe Ukraine off the map,” Biden said in his welcome to NATO member states to the summit, referring to the Russian president.

“Ukraine can and will stop Putin. Today, NATO is stronger than it’s ever been in its history.”

Biden has rebuffed calls to step aside in his race against 78-year-old Trump, vowing to beat him in November. So far, he has maintained the public support of most of his party’s elite.

He closed his remarks by surprising NATO Secretary-General Jens Stoltenberg with the Presidential Medal of Freedom, clasping the highest US civilian award around the Norwegian politician’s neck and crediting him with reviving the 32-member alliance.

The centrepiece of the NATO summit is set to be new commitments of military and humanitarian aid to Ukraine. US Secretary of State Antony Blinken said the summit would “further strengthen” the war-torn country’s path to NATO membership.

Biden and the leaders of Germany, Italy, the Netherlands and Romania issued a joint statement with Ukrainian President Volodymyr Zelensky announcing the delivery of five more Patriot and other strategic air defence systems to protect Ukrainian cities, civilians and soldiers.

They said additional strategic air defence systems would be announced this year.

Biden will also hold a rare solo press conference on Thursday.

-with AAP