Donald Trump has falsely claimed he has the “absolute right” to ask foreign countries to investigate his opponents over alleged corruption.
“As the president of the United States, I have an absolute right, perhaps even a duty, to investigate, or have investigated, CORRUPTION, and that would include asking, or suggesting, other countries to help us out!” Mr Trump said, in a tweet posted during the early hours of Friday.
The controversial leader’s comment comes after Democrats accused him of illegally pressuring Ukraine to probe unsubstantiated allegations about the Biden family.
Democrats announced plans to impeach the president after a whistleblower complained about a 25 July call between Mr Trump and the leader of Ukraine.
In a summary of the call Mr Trump suggested Ukraine should investigate Joe Biden’s son Hunter, who served on the board of a Ukrainian company.
The president also delayed around $250m (£202m) in military aid for Ukraine.
Mr Trump has denied any wrongdoing but on Thursday also called on China and Ukraine to investigate the Bidens.
“[Ukraine] should investigate the Bidens,” Mr Trump told journalists.
“And by the way, likewise, China should start an investigation into the Bidens.”
Joe Biden, the former vice-president, is one of the Democratic frontrunners for 2020. A Ukrainian investigation into a company called Burisma, where Hunter Biden served on the board, no evidence of criminal wrongdoing by its owner.
The investigation was subsequently closed, but on Friday, Ukraine's current chief prosecutor announced that it was reviewing the closure of criminal investigations.
A series of text messages, handed over by one diplomat to a congressional investigative committees, reveal that envoys were pressuring Ukraine to publicly announce an investigation.
Under the Federal Election Campaign Act it is illegal in the US to accept foreign aid to interfere with elections in the US. In an apparent warning to the president, Ellen Weintraub, head of the Federal Election Commission, retweeted on Thursday a post she first published in June about receiving foreign help in elections.
“Let me make something 100 per cent clear to the American public and anyone running for public office: It is illegal for any person to solicit, accept, or receive anything of value from a foreign national in connection with a U.S. election,” she said.
“This is not a novel concept.”
The president is not exempt from the scope of the law.
Additional reporting by agencies