Immigration and Customs Enforcement (ICE) agents are allegedly planning mass raids across the country beginning “next week,” according to Monday night tweets from President Donald Trump.

“Next week ICE will begin the process of removing the millions of illegal aliens who have illicitly found their way into the United States,” Trump wrote. “They will be removed as fast as they come in.”

Large scale ICE operations are kept under wraps so as to avoid tipping off those who could be a target. When Trump’s threat became public, no one was more surprised than Trump’s own immigration law enforcement agents, who told The Washington Post they were stunned Trump would make such an announcement. One former senior ICE official told Buzzfeed News it puts officer safety at risk.

A mass raid has been in the works within the administration for a long time, and is partly why many former top officials at the Department of Homeland Security (DHS) left the administration earlier this year. According to The Washington Post, the plan consisted of arresting immigrant families in 10 major cities across the country, specifically targeting immigrants who failed to show up for their day in court.

Former DHS Secretary Kirstjen Nielsen and Trump’s then-rumored pick for ICE chief Ron Vitiello opposed the plan, saying ICE agents lacked the preparation for a coordinated raid of that scale, that it would take away resources from the border, and that it would cause public outrage.

Arresting “millions” of undocumented immigrants in a week, as Trump suggested in his Monday tweet, would be unprecedented for the agency. The highest yearly number of deportations from ICE was around 400,000. Furthermore, a mass operation of that scale would require much more resources than the agency currently has access to.

Enforcement Removal Operations (ERO), the arm of ICE that does the majority of arresting and deporting, only has around 6,000 agents. It would possibly need to pull from its investigations unit, Homeland Security Investigations (HSI), to conduct the operation — pulling them off assignments related to cyber crimes and human trafficking. It could also potentially require DHS to pull agents from the so-called “national emergency” at the U.S.-Mexico border.

The administration claims its operation would focus squarely on the roughly one million people who have missed their court hearings and haven’t left the country despite being issued a final order of removal. The vast number of immigrants, however, do make their court appearances, and pending final orders of removal are usually the result of the government’s failure to adequately notify the person charged. For example, as ThinkProgress has previously reported, an undocumented mother from Colombia who lived in the United States for over a decade was deported because she missed a check-in with ICE, despite having a valid work visa. Her immigration lawyer had committed suicide and notifications from the government never made their way to her mailbox.

A raid of the magnitude the administration is proposing would also have a profound impact on the economy for which Trump loves to take credit. Undocumented immigrants pay an estimated $11.6 billion a year in taxes. Deporting millions would mean bills going unpaid and groceries not being bought. The total spending power of immigrants is estimated to be over $900 billion.

In spite of this, current administration officials support a mass raid. White House Senior Adviser Stephen Miller, ICE Deputy Director Matthew Albence, and ICE Acting Director Mark Morgan believe one dramatic operation within the interior of the United States is needed to show immigrants that the administration is serious about immigration enforcement.

Publicly announcing ICE raids in the way Trump did, however, is particularly hypocritical, considering in 2018, he and other top administration officials threatened Oakland Mayor Libby Schaaf with criminal charges for warning city residents of potential raids. 

“The Oakland mayor’s decision to publicize her suspicions about ICE operations further increased that risk for my officers and alerted criminal aliens — making clear that this reckless decision was based on her political agenda with the very federal laws that ICE is sworn to uphold,” then-ICE Deputy Director Thomas D. Homan said at the time.

Homan has since retired from his position at ICE, but as recently as last week Trump said he would be his “border czar.” Homan meanwhile called the announcement premature and said he would need to think it over first.

Schaaf, for her part, responded to Trump’s public announcement Monday night, signaling a potential action from the city of Oakland to protect those who may be targeted.

“If you continue to threaten, target and terrorize families in my community… and if we receive credible information… you already know what our values are in Oakland — and we will unapologetically stand up for those values,” she wrote.