President Donald Trump delivered an 11th-hour policy speech just days before the critical midterm elections in which he called for hard-line immigration measures, doubling down on his pre-election messaging focused on a migrant caravan traveling through Mexico toward the U.S. southern border.

"At this very moment, large, well-organized caravans of migrants are marching toward our southern border. Some people call it an invasion. It's like an invasion," he said at the White House Thursday.

"Under this plan, illegal aliens will no longer get a free pass into the country by lodging meritless claims in seeking asylum," he added. "...We will not allow our generosity to be abused by those who would break our laws."

Most prominently, Trump said he plans to block immigrants from claiming asylum at any location other than a legal port of entry, and to hold them in detention until they have an asylum hearing. He said his administration is ready to hold both adults and their children together in "tent cities" along the border until those hearings take place.

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Trump insisted that both of those measures would be legal, though he provided little detail as to how the proposed changes could be implemented. Under current asylum law, immigrants are able to claim asylum anywhere inside the U.S. Immigrants often enter away from ports of entry which can suffer from large backlogs.

Meanwhile, the Zadvydas v. Davis court decision means that adult immigrants cannot be detained for longer than six months unless they've committed another crime aside from illegal entry. The Reno v. Flores court decision limits the time that children can be held to 20 days.

Trump made a number of misleading or false statements during the speech, including about the total number of undocumented immigrants are in the U.S. and about the progress of his wall along the nation's southern border.

As he has made immigration the central focus of his end-of-campaign messaging, Trump claimed that the migrant caravan traveling through Mexico — consisting of several thousand members — was seeking to invade the country. The president repeatedly called the group of migrants "an invasion," and claimed no one was questioning that assertion, though many are.

Trump also seemed to lay out the conditions where the thousands of troops to be deployed to the border would be able to fire at migrants seeking entry. Trump said that should any migrants "throw rocks at our military, our military fights back."

Earlier this week, Trump announced that the Pentagon would deploy 5,200 troops to deter a caravan of largely Honduran migrants at the southern border. On Wednesday, he suggested he could send as many as 15,000.

He made the issue of birthright citizenship a campaign issue this week with his quickly-disputed claim he could unilaterally eliminate the constitutionally-rooted right. The president also released an ad on Wednesday in which he, without evidence, linked the issue of immigration to a case in which a man was given the death penalty for killing two California police officers in 2014 — an incident which he has used in previous campaign ads.

NBC News previously reported that the Trump administration is drafting an executive action that would make it far more difficult for Central Americans seeking asylum to gain entry at the U.S.-Mexico border.

The speech was expected to be given earlier this week but was postponed after a shooting at a Pittsburgh synagogue this past weekend, which killed 11 people.

After speaking, the president departed for Columbia, Missouri for an evening campaign rally.