President Trump doubled down on his incorrect characterization of comments by London Mayor Sadiq Khan on Monday morning, escalating his feud with the U.K. leader after deadly terrorist attacks in his city over the weekend.

Trump first tweeted over the weekend about Khan's comments to Londoners telling them there was “no need to be alarmed” by an increase in police presence in the streets. Trump implied in his tweet that the mayor was referring generally to the threat of terrorism.

In a new tweet on Monday, Trump criticized Khan again and accused the “mainstream media” of attempting to cover for him.

“Pathetic excuse by London Mayor Sadiq Khan who had to think fast on his ‘no reason to be alarmed’ statement,” Trump tweeted. “MSM is working hard to sell it!”

Trump's tweets came after a morning in which he insisted that his travel ban, which attempted to block immigration from six predominantly Muslim countries before it was halted by federal courts, was a necessary measure to prevent attacks like the one that occurred in London.

In responding to the terrorist attacks in London over the weekend, Trump blamed “political correctness” for putting citizens in the United States, and presumably London, at risk.

“We must stop being politically correct and get down to the business of security for our people,” Trump tweeted. “If we don't get smart it will only get worse.”

Khan, who is London's first Muslim mayor, had criticized Trump's rhetoric toward immigrants and Muslims during the U.S. presidential campaign.

But over the weekend, his office issued a statement tersely declining to respond to Trump's “ill-informed tweet.”