President Donald Trump pledged on Monday night to begin deporting millions of undocumented Central American immigrants who have entered the United States illegally and praised Mexico’s renewed efforts to prevent migrants from crossing into the U.S.

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In a tweet Monday night, the president wrote, “Next week ICE will begin the process of removing the millions of illegal aliens who have illicitly found their way into the United States. They will be removed as fast as they come in.” He went on to speak highly of Mexican immigration control, writing, “Mexico, using their strong immigration laws, is doing a very good job of stopping people … long before they get to our Southern Border. Guatemala is getting ready to sign a Safe-Third Agreement.” He finished up his Twitter tirade by attacking the Democrats, ranting, “The only ones who won’t do anything are the Democrats in Congress. They must vote to get rid of the loopholes, and fix asylum! If so, Border Crisis will end quickly!”

Trumps’ tweets broke with a longstanding Immigrations and Customs Enforcement (ICE) protocol of not discussing operations before they are conducted. Some ICE officials worry that the president’s tweets, which practically amount to a warning, will prevent the effectiveness of the planned deportation crackdown. This most recent leak is just another instance of questionable information handling by Trump that has made his advisors nervous about his ability to keep state secrets. The same day as Trump’s ICE tweet, he made another post denying the New York Times’ report that officials in the Pentagon had refrained from informing Trump of U.S. cyberattacks on Russia out of fear that the president would “discuss it with foreign officials.”

Trump divulged similar information in 2017, when he told the Russian ambassador about a sensitive U.S. operation in Syria, one of Russia’s close allies.