President Donald Trump is off to a rocky start in the United Kingdom.

President Trump’s state visit to the U.K. on Monday June 3 started off with a combative series of tweets, including a suggestion to boycott AT&T in protest of CNN, a subsidiary of the telecom giant, for its antagonistic coverage of his administration.

The president also called Sadiq Khan, the mayor of London, a “stone cold loser” after the mayor wrote an op-ed in the Observer saying the U.K. was being “un-British” by hosting a leader ”whose divisive behavior flies in the face of the ideals America was founded upon — equality, liberty and religious freedom.”

The president complained shortly after arriving that since Fox News was unavailable in the U.K., he was forced to watch CNN. “Just arrived in the United Kingdom. The only problem is that @CNN is the primary source of news available from the U.S. After watching it for a short while, I turned it off. All negative & so much Fake News, very bad for U.S. Big ratings drop. Why doesn’t owner @ATT do something?”

President Trump has frequently derided CNN as “fake news.” His administration allegedly pressured the Department of Justice to block the merger of AT&T and Time Warner, which previously owned CNN. According to the New Yorker’s Jane Mayer, the Trump administration didn’t seek to stop the merger for genuine antitrust concerns but because the president believed it would give more power to CNN. President Trump’s tweet to 60 million followers calling to boycott the telecom giant on Monday represents a more direct strategy to limit the network’s influence.

“I believe that if people stoped [sic] using or subscribing to AT&T, they would be forced to make big changes at CNN, which is dying in the ratings anyway. It is so unfair with such bad, Fake News! Why wouldn’t they act,” the president tweeted. “When the World watches @CNN, it gets a false picture of USA. Sad!”

Critics argue it is undemocratic and unconstitutional to allow the president’s personal views to shape regulations on the press. “For the president to try to tilt the marketplace in favor of one outlet or another is dangerous to our democracy and the marketplace of ideas,” Gene Kimmelman, a former Justice Department antitrust official, told the Washington Post.

Historian Jon Meacham agreed, saying, “For a president to call for punitive action against a corporation in an effort to shape news coverage is, to say the least, highly unusual. It’s the kind of behavior more commonly associated with authoritarian regimes, not democratic ones.”

The president concluded his first day in the U.K. with a dinner in Buckingham Palace, praising the queen and the British people in his toast. Outside of the palace, protesters from Amnesty International and the group Led by Donkeys projected anti-Trump images on London landmarks like Big Ben and the Tower of London.

The White House says the president’s visit to the U.K. will focus on discussing a new bilateral trade agreement as the country attempts to exit the European Union, as well international security in regards to tensions with Iran, China and North Korea. He is also there to commemorate the 75th anniversary of D-Day in WWII.