US President Donald Trump has lashed out at congressional Democrats after they vowed to summons the White House to produce documents this week.
Committees are demanding documents relating to the administration’s dealings with Ukraine, which is now at the heart of an impeachment inquiry.
The president accused Democratic leaders of dishonesty and even treason.
Democrats have defended the inquiry – which focuses on a phone call between Mr Trump and the Ukrainian president.
Warning: this report contains strong language
What did President Trump say?
During a joint news conference with Finnish President Sauli Niinistö, Mr Trump called Mr Biden and his son, Hunter, “stone-cold corrupt”.
Mr Trump directed much of his anger towards House Intelligence Committee Chairman Adam Schiff, calling him “shifty Schiff, “a lowlife” and saying he “should resign from office in disgrace”.
He added: “Frankly, they should look at him for treason.”
Mr Trump also stated that he believed Mr Schiff had “helped write” a complaint about the call filed by a whistleblower, without offering evidence.
The US president told reporters that only “legitimate” whistleblowers should be protected.
“This country has to find out who this person was, because that person’s a spy, in my opinion,” Mr Trump said.
He labelled the entire inquiry a “hoax” and a “fraudulent crime on the American people” while maintaining he would “always co-operate” with Congress.
The US president also sparred at the White House with a Reuters correspondent, who asked him what he considered treasonous.
As the Finnish leader looked on, Mr Trump said “there are those who think I’m a very stable genius” and said he “probably will be bringing a lot of litigation” against those who participated in the Russia investigation.
When the reporter pressed Mr Trump, the US president cut him off, saying: “Don’t be rude.”
Earlier, Mr Trump raged at the most powerful elected Democrat, House of Representatives Speaker Nancy Pelosi, and Mr Schiff on Twitter, accusing Democrats of focusing on “BULLSHIT”.
Mr Trump said Mrs Pelosi should focus on her own city, San Francisco, which he described as a “tent city” of homeless people.
What’s the inquiry about?
The impeachment inquiry – which may seek to remove Mr Trump from office – stems from the whistleblower’s complaint about his 25 July phone conversation with President Volodymyr Zelensky.
In the call, Mr Trump pressed for an investigation of his Democratic political rival Joe Biden and his son, who worked for a Ukrainian gas firm. No evidence of wrongdoing by the Bidens has come to light.
Democrats have pointed out the call with the newly elected Mr Zelensky took place at the same time Mr Trump decided to withhold military aid from Ukraine.
Mr Trump’s opponents say he was pressuring a vulnerable US ally to interfere in the 2020 US election for the US president’s personal benefit.
What did Democrats say?
Democrats have accused the White House of blocking congressional inquiries and refusing to respond to record requests, which has prompted the subpoena threat this week.
House oversight committee chairman Elijah Cummings said in a memo: “I do not take this step lightly.
“Over the past several weeks, the committees tried several times to obtain voluntary compliance with our requests for documents, but the White House has refused to engage with – or even respond to – the committees.”
The subpoena will request documents on Mr Trump’s call with Ukraine and any related items from acting White House chief of staff Mick Mulvaney.
Mrs Pelosi and Mr Schiff held a joint news conference on Wednesday, defending the impeachment proceedings.
“We’re not fooling around here,” Mr Schiff said, adding that Democrats did not want the inquiry to “drag on”.
He also criticised the president’s comments against the whistleblower as “a blatant effort to intimidate witnesses” and “an incitement of violence”.
Mr Schiff has also issued a statement saying his committee never reviewed or received the whistleblower’s complaint in advance, as Mr Trump claimed.
Quick facts on impeachment
Impeachment is the first part – the charges – of a two-stage political process by which Congress can remove a president from office
If the House of Representatives votes to pass articles of impeachment, the Senate is forced to hold a trial
A Senate vote requires a two-thirds majority to convict – unlikely in this case, given that Mr Trump’s party controls the chamber
Only two US presidents in history – Bill Clinton and Andrew Johnson – have been impeached but neither was convicted and removed
President Nixon resigned before he could have been impeached