US President Donald Trump has denied asking the justice department to clear him of wrongdoing over a phone call with Ukraine's president that is at the heart of an impeachment inquiry.
US media say Attorney General William Barr declined Mr Trump's request to hold a press conference to declare no laws were broken.
Mr Trump called the story a "con job".
The Democratic-led inquiry hinges on whether Mr Trump pressured Ukraine on that call to investigate a rival.
Mr Trump denies using US military aid as a bargaining chip to prod Ukraine's President Volodymyr Zelensky into launching a corruption investigation against Democratic White House contender Joe Biden.
According to a rough transcript, Mr Trump suggested that Mr Zelensky work with Mr Barr during the call.
A justice department spokeswoman later said Mr Barr was unaware he had been mentioned by the president until "several weeks" after the call.
The US president, a Republican, has repeatedly insisted his call with Ukraine's leader was "perfect".
"The Justice Department already ruled that the call was good," Mr Trump wrote on Twitter on Thursday.
The president appeared to be referring to a statement issued by the department in September, saying it had "reviewed the official record of the call and determined, based on the facts and applicable law, that there was no campaign finance violation and that no further action was warranted".
After the Washington Post published a story about Mr Trump's alleged request to Mr Barr, the president called the report "degenerate". Since then other media, including the Wall Street Journal, the New York Times and the BBC's US partner CBS News, have run similar stories.
What is the latest in the impeachment probe?
House Democrats will hold the first public hearings next week. One of the first to appear will be Bill Taylor, acting US ambassador to Ukraine.
Mr Taylor said in a private hearing last month it was his "clear understanding" that the president had withheld nearly $400m (£310m) in US military aid because he wanted Ukraine to investigate discredited corruption claims against Democrat Joe Biden and his son.
Also on Thursday, the committees leading the impeachment inquiry released a transcript of a closed-door deposition by Deputy Assistant Secretary of State George Kent last month.
In his testimony, Mr Kent echoed criticism of the role played by Mr Trump's personal lawyer Rudy Giuliani - who many witnesses have accused of being behind the drive to get Ukraine to announce an investigation into the Bidens.
Mr Kent said Mr Giuliani had been conducting a "campaign of full of lies and incorrect information".
In August, an anonymous intelligence whistleblower wrote a letter expressing concern over the 25 July Trump-Zelensky call, which took place shortly after Mr Trump withheld military aid to Ukraine.
The whistleblower's identity has so far been closely guarded by Democrats, amid demands from their Republican colleagues to hear from the individual directly. Lawyers for the whistleblower have told investigators their client is only willing to answer written questions.
The conservative Fox News network, which is generally supportive of Mr Trump, has reportedly instructed its hosts not to identify the purported whistleblower. Other right-wing media outlets have already done so.
Most media organisations, including the BBC, have not named the source.