Trump attacks Britain's public healthcare system

"The Democrats are pushing for Universal HealthCare while thousands of people are marching in the UK because their U system is going broke and not working," he wrote in an early morning tweet.

"Dems want to greatly raise taxes for really bad and non-personal medical care. No thanks!"

The tweet came after thousands of people marched through central London on Saturday in support of the National Health Service, which is straining under the weight of winter demand.

NHS staffing levels have been in crisis for months, an issue made worse by a winter flu outbreak.

Despite its current woes, the public health service, which was created after World War II, is a revered institution and Trump's comments are likely to stoke resentment.

The "special relationship" between Britain and the United States has shown some signs of strain since Trump came to office a year ago.

British Prime Minister Theresa May was the first foreign leader to visit Trump following his inauguration in January last year, when she invited him to make a state visit to Britain, hosted by Queen Elizabeth II.

The trip has been delayed, however, and Trump recently pulled out of a plan to open the new US embassy in London, a move British officials blamed on threats of mass protests.

Trump has also angered the British with previous controversial tweets, including retweeting a British extremist group's anti-Muslim propaganda and sparring with London mayor Sadiq Khan following a terror attack in the British capital.

It is not certain why Trump chose to attack the NHS two days after the London protests.

Trump's own attempts to reverse his predecessor's healthcare reform, known as Obamacare, twice ended in failure, before his party succeeded in eliminating a key element -- the so-called "individual mandate" as part of tax reform.

The measure required individuals to buy health insurance as a way to lower costs by ensuring that healthy people were part of the insurance pool.

One possible explanation for Trump's criticism was an appearance by Brexit champion Nigel Farage, a former leader of the UK Independence Party and a personal friend of Trump, on Fox News Monday when he talked about the protests.