Speaking in Florida Thursday, Trump blasted his accusers as "maniacs" pursuing "impeachment crap" as he sought to turn the tables on a probe that threatens to make him only the third US president ever impeached in the House of Representatives, and face a trial in the Senate, AFP reported.
As a former State Department diplomat testified behind closed doors in Congress on his role in the Ukraine scandal, Trump doubled down by calling for Ukraine President Volodymyr Zelenskiy and Chinese leader Xi Jinping to go after Biden, who leads the race for the Democratic presidential nomination next year.
"I would say that President Zelenskiy, if it were me, I would recommend that they start an investigation into the Bidens," Trump told reporters outside the White House.
"Likewise, China should start an investigation into the Bidens, because what happened in China is just about as bad as what happened with Ukraine."
Asked if he would request Xi do the same, Trump replied, "It's certainly something we can start thinking about."
Adam Schiff, the Democrat leading the impeachment probe in the House of Representatives, said Trump was acting "with impunity" in the face of the law.
"Once again we have a president of the United States suggesting, urging a foreign country to interfere in our presidential elections," Schiff said.
Trump is accused of pushing Zelenskiy to investigate the US leader's 2020 election rival Joe Biden in return for $400 million in military aid, in a mushrooming scandal that has engulfed the White House, State Department and Justice Department.
With Congress due to hear from intelligence community inspector general Michael Atkinson, the White House was reeling from the release of text messages illustrating US officials' concerns about the administration's attempt to push Kiev into investigating Biden.
When a whistleblower filed a complaint in August alleging that Trump had pressured Ukraine's president to dig up dirt on Biden, it was Atkinson that deemed it a matter of "urgent concern" and passed it on to the Justice Department.
Among the trove of texts released by the House intelligence committee late Thursday, was a message from former US special envoy to Ukraine Kurt Volker to a Zelenskiy aide, saying that that the Ukrainian president should open the investigation in return for a visit to the White House.
"We have ample evidence now that there was a requirement that President Zelenskiy investigate the 2016 election, and the Bidens, if he wanted to get a meeting," Democrat Eric Swalwell said after Volker testified for eight hours.
It is illegal for a US national to seek foreign help in a domestic election, regardless of whether an inducement is offered.
Trump's frustration and anger over the scandal have boiled over in a series of increasingly erratic and outlandish public appearances and Twitter rants in which he flitted between defiance and conspiratorial paranoia.
"As President I have an obligation to end CORRUPTION, even if that means requesting the help of a foreign country or countries," Trump tweeted Friday.
"It is done all the time. This has NOTHING to do with politics or a political campaign against the Bidens. This does have to do with their corruption!"
Trump alleges that Biden, as vice president in 2014, tried to block a Ukraine corruption probe into his son Hunter's business partner, a Ukraine gas tycoon, using US aid as leverage.
He also alleged Hunter used his stature to raise $1.5 billion in 2013 from China for a new investment vehicle in Beijing.
He made "millions" off these investments, Trump alleges.
The record in Ukraine however shows that there was no corruption probe of Hunter Biden's partner to be blocked, and that the United States and allies all viewed Kiev's since-removed corruption prosecutor at the time as himself deeply compromised.
In China, according to multiple media reports, a business associate of Hunter Biden obtained an investment license that did not include Biden's name, and only raised several million dollars.
Hunter Biden put up $420,000 for a minority interest, and has not received any compensation or return on it, his lawyer told the Washington Post.
Joe Biden's campaign called Trump's comments already-debunked "conspiracy theories" and accused him of "a grotesque choice of lies over truth and self over the country."
"Mr. President, you cannot extort foreign governments to help you win reelection. It's an abuse of power. It violates your oath of office. And it jeopardizes our national security," Biden tweeted separately.