Crying foul over timing, President Donald Trump on Monday accused Democrats of scheduling this week’s impeachment hearing to undercut him during his trip abroad for a NATO leaders’ meeting.

Mr Trump, who arrived in London late Monday for two days of meetings which come at a crucial moment for the 70-year-old military alliance. He called the trip “one of the most important journeys that we make as president” before departing Washington, and noted Democrats had long known about the meeting.

The president lashed out at Democrats again soon after arriving in the UK.

He wrote on Twitter that he had read the Republican report designed to counter Democrats’ impeachment case on his flight. The report, which was obtained by The Associated Press, called Mr Trump’s hesitation to provide military aid to Ukraine “entirely prudent.”

“Prior to landing I read the Republicans Report on the Impeachment Hoax. Great job! Radical Left has NO CASE. Read the Transcripts,” Mr Trump wrote. “Shouldn’t even be allowed. Can we go to Supreme Court to stop?”

It was not immediately clear under what legal grounds Mr Trump was calling for the court’s involvement.

Mr Trump’s trip comes amid ongoing quarrels over defence spending by NATO allies and widespread anxiety over the president’s commitment to the alliance.

The president said his trip would be focused on “fighting for the American people”. But in the more than two months that the impeachment inquiry has been under way, he has constantly drifted back to what he frames as the Democrats’ unfair effort to overturn the results of his 2016 election.

The House Judiciary Committee is scheduled to hold a hearing on Wednesday on the constitutional grounds for impeachment before Mr Trump wraps up at the NATO meeting.

NATO summit 2019
US President Donald Trump and his wife Melania are greeted by United States Ambassador to the United Kingdom Robert “Woody” Johnson as they arrive at Stansted Airport ahead of the NATO summit (Joe Giddens/PA)

Mr Trump, Secretary of State Mike Pompeo, White House counsel Pat Cipollone and presidential counsellor Kellyanne Conway all complained about the timing, with Mr Pompeo saying the hearings would “distract America’s president from his important mission overseas”.

Mr Trump insists he is solely focused on scoring domestic and foreign policy wins, including revamping NATO so that allies spend more on defence. But he has often appeared consumed by the day-to-day battle against impeachment.

In recent days he has repeatedly lashed out about the “impeachment hoax” and the “scam” inquiry, even delving into impeachment at a ceremony to celebrate NCAA athletes and at last week’s annual Turkey pardon.

White House aides say the summit offers Mr Trump an opportunity to counter the impeachment narrative in Washington and demonstrate to voters he is keeping a business-as-usual approach while Democrats concentrate on the probe.

But soon after Air Force One departed, Mr Trump took to Twitter to slam “Do Nothing Democrats” for scheduling the hearing during the NATO meeting as “Not nice!””

House Speaker Nancy Pelosi, in Madrid for a UN conference on climate change, declined to comment about the impeachment inquiry, saying, “When we travel abroad, we don’t talk about the president in a negative way. We save that for home.”

Mr Trump is only the fourth US president in history to face an impeachment inquiry. The gravity of impeachment is likely to play into the calculus of how other global leaders engage the president going forward, in the view of some analysts.

“In one sense impeachment is weakening his hand diplomatically,” said Ted Galen Carpenter, a senior fellow for defence and foreign policy studies at the Cato Institute in Washington. “For a normal president, it would be seen as a substantial problem. For Donald Trump, he’s going to try to blow right through it and act is if that’s not a relevant factor.”

The NATO leaders meeting is a complicated backdrop for Mr Trump to make his first extended overseas visit — he made a quick Thanksgiving visit to US troops in Afghanistan — since Democrats launched the impeachment inquiry.

The president has repeatedly criticised fellow NATO members and complained that too few nations are on track to meet the alliance goal of spending at least 2% of GDP on defence by 2024.

French President Emmanuel Macron recently lamented that a lack of US leadership was causing the “brain death” of the alliance.