Trump asked about shooting migrants crossing border in the legs: Sources Trump denied a news report that he wanted to build a moat with alligators.

Frustrated with a record number of people seeking asylum at the U.S.-Mexico border this spring, President Donald Trump at one point asked in a private meeting with close aides whether the U.S. could shoot migrants below the waist to slow them down.

The account, first reported in a book excerpt released by the The New York Times on Tuesday, was confirmed to ABC News by a senior administration official who was in the room at the time, as well as several other sources who were later briefed on the conversation.

According to two sources familiar with the matter, Trump in private meetings raised the prospect of shooting migrant families seeking asylum at the border as early as November 2018. He also floated a similar idea publicly at one point, suggesting that rocks thrown by migrants will be considered a firearm and potentially warrant lethal force.

Sources interviewed by ABC News say Trump’s aides discouraged the idea of shooting unarmed migrants and it was never acted upon. But Trump remained focused on the idea, bringing it up again in the private Oval Office meeting in March 2019, when the number of undocumented migrants arriving at the border topped 100,000 for that month alone.

The detail of shooting migrants below the waist are included in a new book “Border Wars: Inside Trump’s Assault on Immigration,” by Times reporters Julie Hirschfeld Davis and Michael D. Shear. According to Davis and Shear, the president also talked to aides about building an electrified border wall, as well as a “water-filled trench, stocked with snakes or alligators, prompting aides to seek a cost estimate.”

In a tweet Wednesday, Trump denied the allegations about the trench and the electrified fence, but did not address the idea of shooting migrants.

"I may be tough on Border Security, but not that tough," he wrote. "The press has gone Crazy. Fake News!" he tweeted, initially misspelling "Moat" as "Moot." It was later corrected.

Attending the meeting was then-Homeland Security Secretary Kirstjen Nielsen, who resigned in April. It was widely reported at the time that Trump didn’t think Nielsen had done enough to curb the tide of asylum seekers, which is expected to fall shy of 1 million people this year alone.

Trump’s repeated question on allowable use of force underscores the extreme lengths the president has been willing to consider to address a signature issue for the president. Trump frequently describes people coming across the border as part of an "invasion" and people who are criminals.

Nielsen was replaced by acting Homeland Secretary Kevin McAleenan, who has overseen a reduction in border numbers in recent months in part because of a new policy – initiated by Nielsen – that forces asylum seekers to wait in Mexico while their claims are processed. Human rights groups say the policy has created a humanitarian crisis south of the U.S. border, where migrant families face scarce food and clean water and fear for their safety.

In an interview with The Washington Post, McAleenan expressed frustration with “the tone” on immigration in general.

“What I don’t have control over is the tone, the message, the public face and approach of the department in an increasingly polarized time,” he told the Post. “That’s uncomfortable, as the accountable, senior figure.”

“I think the words matter a lot,” McAleenan said. “If you alienate half of your audience by your use of your terminology, it’s going to hamper your ability to ever win an argument.”

McAleenan did not immediately respond to a request for comment.

___ ABC News' Ben Gittleson and Quinn Owen contributed to this report.