A report by the judiciary committee setting out the legal and historical basis for impeachment comes ahead of Monday’s public hearing to consider evidence against Mr Trump.
A vote on articles of impeachment could be held as early as next week.
On Saturday, Mr Trump again described the process as a “witch-hunt”.
The impeachment process began in September after an anonymous whistleblower complained to Congress about a July phone call by Mr Trump to the president of Ukraine, in which the president appeared to tie US military assistance to Ukraine launching investigations which would help him politically.
Democrats say that that this amounted to inviting a foreign power to intervene in the US election to help the president win another term.Hong Kong pro-democracy protesters out in force