Trump Seizes on London Attack to Push for Expanding a Travel Ban

The president’s proposed restrictions have faced legal challenges and drawn criticism because of concerns that they amount to discrimination based on religion.

WASHINGTON — President Trump on Friday used an unfolding terrorist attack in London to revive his push for a travel ban for people from predominantly Muslim countries, an effort that has been hampered by United States courts.

In a series of early-morning Twitter posts, Mr. Trump said the London subway attack had been the work of “a loser terrorist” and suggested that those behind the assault had been “in the sights” of the British authorities. The small explosion on a crowded Underground train during morning rush hour in the capital on Friday wounded at least 22 people, and the police in the city said they were treating the episode as terrorism.

It was not immediately clear who was behind the attack or whether the assailant or assailants had been on the radar of British intelligence, as Mr. Trump suggested.

Mr. Trump also tweeted that his administration had already “made more progress” against the Islamic State than President Barack Obama’s administration had in eight years. In a string of tweets about the London attack, Mr. Trump called for being “proactive & nasty” to fight terrorists.

He did not immediately offer condolences to the British people.

Mr. Trump’s travel ban, proposed in January and revised in March, has faced legal challenges and drawn criticism from around the world because of concerns that it amounts to discrimination based on religion.