WASHINGTON — When a federal judge blocked President Trump’s first attempt to impose a travel ban on seven majority-Muslim nations, Mr. Trump warned of “death & destruction” from dangerous people who “may be pouring into our country.”

“Courts must act fast!” he implored on Twitter.

But in the 128 days since, the president’s administration has exhibited little urgency of its own.

Mr. Trump’s lawyers have moved slowly in responding to legal challenges to the White House’s initial and revised travel bans. And immigration experts say the administration has not taken steps it could have — even while the latest ban is tied up in the courts — to achieve the restriction’s stated goal: to tighten the vetting of people trying to get into the United States.

The result has been that almost halfway through his first year in office, Mr. Trump has made few changes to the way people enter the United States from the countries he has deemed the most dangerous, despite his frequent campaign promises to institute “extreme vetting.”