The lawyers for a whistleblower whose complaint triggered a US presidential impeachment inquiry say Donald Trump’s words are endangering their client.
Since the transcript of his call with the president of Ukraine was revealed, Mr Trump has called for the anonymous whistleblower to be unmasked.
Democrats say the whistleblower will testify to Congress “very soon” once steps are taken to protect identity.
Mr Trump has suggested his opponents could be arrested for “treason”.
A transcript of a call Mr Trump made to Ukraine’s new President Volodymyr Zelensky shows he urged him to investigate discredited corruption allegations against former vice-president and 2020 presidential candidate Joe Biden as well as his son.
The call is now at the centre of an effort by Democrats that could see Mr Trump expelled from office, but doing so would require members of his Republican party to turn against him.
On Sunday, Democratic House Intelligence Committee Chairman Adam Schiff said Congress was finalising plans to have the whistleblower testify to Congress in private