By Veronica Stracqualursi, Priscilla Alvarez and Geneva Sands, CNN

President Donald Trump announced Saturday that he's delaying US Immigration and Customs Enforcement raids that were planned to take place Sunday in 10 major US cities.

"At the request of Democrats, I have delayed the Illegal Immigration Removal Process (Deportation) for two weeks to see if the Democrats and Republicans can get together and work out a solution to the Asylum and Loophole problems at the Southern Border," Trump said on Twitter Saturday. "If not, Deportations start!"

Earlier in the day, Trump defended the raids, arguing that targeted families have been running from the law.

"The people that Ice will apprehend have already been ordered to be deported," Trump tweeted. "This means that they have run from the law and run from the courts. These are people that are supposed to go back to their home country. They broke the law by coming into the country, & now by staying."

ICE is planning on arresting and deporting approximately 2,000 migrant families with court-ordered removals in 10 cities beginning Sunday, a senior immigration official told CNN. Trump told reporters as he departed the White House for Camp David Saturday that the raids would begin "during the course of this next week, maybe even a little bit earlier than that."

"These are people that came into the country illegally. They've been served. They've gone through a process. A process of the courts, and they have to be removed from the country," Trump said. "They will be removed from the country."

He characterized the deportation raids as "very good law enforcement people going by the law," and claimed that his administration is "very focused on getting MS-13 out of this country."

"Some cities are going to fight it, but if you notice, they're generally high crime cities. If you look at Chicago, they're fighting it. If you look at other cities, they're fighting it. Many of those cities are high crime cities and they're sanctuary cities," Trump said. "People are tired of sanctuary cities and what it does and the crime it brings."

Raids are planned in Atlanta, Baltimore, Chicago, Denver, Houston, Los Angeles, Miami, New Orleans, New York and San Francisco.

Trump made a vague announcement on Monday that an ICE operation was imminent. He claimed that his administration would be deporting "millions" of undocumented immigrants next week -- disclosing such an operation before it was carried out and surprising some officials within his own administration.

Acting Department of Homeland Security Secretary Kevin McAleenan, however, has been hesitant about elements of the operation, two sources familiar with his thinking told CNN.

CNN reported last month that the administration had been considering deporting migrant families. A source told CNN at the time that McAleenan was resistant to the plan, concerned in part that it could hurt negotiations with congressional Democrats for ICE funding, which has been strapped for resources as well as the political optics.

According to a source familiar with the situation, McAleenan on Friday pulled out of a planned Sunday show appearance on the day the ICE operation is slated to begin, adding to speculation that there's a split with the White House.

A separate source told CNN that McAleenan was at the White House Friday and "not in a good way."

An ardent supporter of Trump's immigration policies, Tom Homan, the former ICE director and now a FOX News contributor, seemed to suggest Saturday that McAleenan leaked information about the upcoming ICE operation to media.

"You got the Acting Secretary of Homeland Security resisting what ICE is trying to do. In the Washington Post, in numerous media outlets, he does not support this operation," Homan said on Fox News, adding, "This leak, which I know where it came from, we all know where it came from. That story only benefits one person, put these officers at greater risk of harm."

Homan, who Trump named "border czar" but has not yet accepted the job, has previously backed McAleenan.

CNN has reached out to McAleenan for comment.

House Speaker Nancy Pelosi on Saturday pushed for Trump to halt the raids, which she called "heartless" and a "brutal action which will tear families apart and inject terror into our communities."

"These families are hard-working members of our communities and our country. The President's action makes no distinction between a status violation and committing a serious crime," Pelosi said in a statement.

On Friday, the cities' mayors spoke out against the raids and expressed support for the migrant families.

"It is unconscionable that the Federal administration is targeting innocent immigrant families with secret raids that are designed to inflict as much fear and pain as possible," said San Francisco Mayor London Breed, who leads a sanctuary city.

Some of the mayors, including Chicago's Lori Lightfoot and Los Angeles Mayor Eric Garcetti, said their city would not assist in the immigration raids.

"No Angeleno should ever have to fear being snatched from their home or separated from their loved ones — and we are doing everything we can to provide immigrant families with the information and support they need," Garcetti said in a statement.

Acting ICE chief Mark Morgan told reporters Wednesday that the goal is "not to separate families," but to deter migrants from illegally crossing the US-Mexico border.

Migrant families, who had received final orders of removal by judges in absentia, were sent letters in February from ICE, asking them to self-report to local ICE offices by March to comply with the orders, Morgan said.

He said ICE and the Justice Department had worked closely together on the family expedited docket and that the "results were very disappointing," claiming that some families failed to show up for their immigration hearings.

Ahead of Sunday's expected deportation sweeps, field agents at local field offices are receiving briefings and trainings, according to a senior immigration official. There are also preparations being put in place for mixed-immigration status families: for example, if a parent is undocumented, but has a US citizen child.

"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 ongoing enforcement operations before the conclusion of those actions," ICE said in a statement Friday.

In the later years of Barack Obama's presidency, the Department of Homeland Security deployed an operation targeting family units due to the uptick in families and unaccompanied minors attempting to cross the border, after initially focusing on felons. It was revived in Trump's first year in office.

This story is breaking and will be updated