On Tuesday afternoon, Mr. Trump repeated that immigration officials planned to conduct a deportation operation next week. “They know. They know,” Mr. Trump said as he left for Florida. “They’re going to start next week and when people come into our country and they come in illegally, they’ll have to go out.”

Immigration laws prevent the Trump administration from immediately deporting asylum-seeking Central American families, who make up a majority of the migrants arrested at the border. The operation planned by ICE officials would instead target those in the interior of the country who have been issued a final removal order or missed their court date.

After the president spoke on Tuesday, Mark Morgan, the acting director of ICE, declined to say whether the agency was planning mass arrests next week. “The president is very clear with what he’s tweeting out is that he wants to maintain the integrity of the system and he wants to make sure that we’re supporting and enforcing the rule of law,” Mr. Morgan said on PBS NewsHour. “And that’s really what this is about.”

A president releasing the timeline of such immigration raids would be unprecedented because it could spread panic in communities and potentially threaten the success of the raids. An operation targeting families also would not immediately result in the deportation of millions of undocumented immigrants, according to officials who were not authorized to speak publicly about the details of the coming operation or Mr. Trump’s tweet.

ICE charters planes that carry only a couple of hundred migrants back to Central America daily.

While roughly a million undocumented immigrants have been issued removal orders, many of them may be appealing their cases and cannot be deported. The roughly 6,000 deportation officers in ICE also do not know the locations of many of the migrants.