President Donald Trump says a nationwide immigration enforcement operation targeting people who are in the United States illegally will begin Sunday.

The sweep has sparked outrage and concern among immigrant advocates. It's set to target people with final orders of removal, including families.

Trump says Immigration and Customs Enforcement officers are focusing on criminals.

He says authorities are specifically looking for those he calls "bad players." But he says the operation also is targeting people who came into the U.S. illegally, and he says that's not fair to those who've been waiting for years to become citizens through a legal process.

The operation is similar to ones conducted regularly since 2003 that often produce hundreds of arrests.

The operation expected in 10 major cities.

It was initially set for late June, but Trump postponed it as Congress worked to pass a $4.6 billion border aid deal.

Activists are circulating information about hotlines for immigrants to call and bolstering know-your-rights training.

U.S. Immigration and Customs Enforcement released this statement: 

Due to law-enforcement sensitivities and the safety and security of U.S. Immigration and Customs Enforcement personnel, the agency will not offer specific details related to enforcement operations. As always, ICE prioritizes the arrest and removal of unlawfully present aliens who pose a threat to national security, public safety and border security. In fact, 90 percent of aliens arrested by ICE’s Enforcement and Removal Operations component in FY2018 had either a criminal conviction(s), pending criminal charge(s), were an ICE fugitive, or illegally reentered the country after previously being removed. However, all of those in violation of the immigration laws may be subject to immigration arrest, detention and – if found removable by final order – removal from the United States.

(The Associated Press contributed to this report.)