A nationwide wave of arrests of immigrants facing deportation will commence this weekend, U.S. President Donald Trump said on Friday, confirming that the plan, intended to discourage a surge of Central American migrants, was on track after a delay.

The operation, to be carried out in 10 cities, is expected to target families that have recently been ordered deported by an immigration court but have not yet left the country.

Trump previously announced the operation on Twitter last month and then postponed it. It is unusual for the government to announce deportation operations ahead of time.

In a typical week, U.S. Immigration and Customs Enforcement (ICE) arrests thousands of immigrants who are staying in the country illegally, according to government data. Most of those arrests are made without any special publicity.

Immigrant advocates have said advance word of the weekend raids could help some of those targeted to evade arrest.

But the president, speaking to reporters at the White House on Friday, said he did not share those concerns, as the deportations were not a secret.

“People are coming into this country illegally, we are taking them out legally,” he said. “If the word gets out, it gets out.”

Trump, who has made cracking down on illegal immigration a centerpiece of his administration, is trying to deal with a surge of mostly Central American families crossing the U.S.-Mexico border. Many families are approaching border officials to seek asylum.

The latest planned arrests would follow widespread criticism of the crowded, unsanitary conditions in which immigrants are being detained along the southwestern border and concerns about children being separated from adults by border officials.