US President Donald Trump lashed out at Democrats for continuing with hearings in the impeachment inquiry while he heads to London. Picture: AP Photo/Alex Brandon

Washington - US President Donald Trump lashed out at Democrats for continuing with hearings in the impeachment inquiry while he heads to London to meet with leaders of NATO member states to mark the alliance's 70th anniversary.

"It's an absolute disgrace what they are doing to our country," Trump said as he prepared to depart Washington for London, noting the NATO meeting was planned well in advance.

The president said he would not be sending lawyers to impeachment inquiry hearings, calling the process a "hoax." 

He vowed to raise the issue of NATO members' defence spending during the leaders' meeting. "They are going to have to do a little more burden sharing," he said, insisting that the status quo has been "unfair" to the US.

On Wednesday, as Trump is due to be wrapping up his trip to London and will likely hold a press conference, the Judiciary Committee at the House of Representatives will start the second phase of the impeachment inquiry.

The Democrats, who control the House, launched the impeachment inquiry in September, accusing the president of abusing the power of his office to pressure Ukraine to investigate his domestic rival, Joe Biden, the Democratic Party's frontrunner for the 2020 nomination.

The second phase of the inquiry will focus on the legal basis for drawing up articles of impeachment.

The first phase, at the intelligence committee, was a fact-finding mission that included public hearings where several witnesses testified they were concerned about the White House's relationship with Ukraine and the possible leveraging of military aid to get dirt on Biden.

dpa