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WASHINGTON — President Donald Trump, urging tougher security measures along the U.S.-Mexico border on Thursday, claimed that women "are being raped at numbers never seen before" while an immigrant caravan is heading toward the U.S.

"Yesterday, it came out where this journey coming up, women are raped at levels that nobody has ever seen before," the president said at a White House tax reform event in White Sulphur Springs, West Virginia. "They don't want to mention that, so we have to change our laws."

"Remember my opening remarks at Trump Tower...Everybody said, 'Oh, he was so tough.' I used the word 'rape,'" the president said.

That was a reference to the announcement of his bid for the White House in 2015. In that speech, Trump disparaged Mexican immigrants, claiming, "They're bringing drugs. They're bringing crime. They're rapists. And some, I assume, are good people."

On Thursday, Trump did not provide any evidence to support his claim that rapes are taking place during the caravan in Mexico of asylum-seekers, nor did he identify the source of his information. The White House did not immediately respond to a request for that information.

Buzzfeed News immigration reporter Adolfo Flores, who has been traveling with the caravan for nearly two weeks, tweeted, "To be clear I haven’t heard of anyone being raped in or around the caravan." The caravan largely ended on Thursday, nowhere near the American border.

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Later, Trump told reporters aboard Air Force One that he was considering sending 2,000 to 4,000 National Guard troops to the border, offering the first potential details about the size of the move since publicly raising the idea — which has been embraced by previous presidents, including George W. Bush and Barack Obama — on Tuesday, and signing a proclamation officially directing it the following day.

Trump began the week warning of dangerous "caravans" of immigrants headed for the U.S. border with Mexico. On Tuesday, he tweeted about "the big Caravan of People from Honduras, now coming across Mexico and heading to our 'Weak Laws' Border."

Trump used the event in West Virginia Thursday, billed as a tax reform roundtable, to discuss border security, immigration and voter fraud. He also took the opportunity to hammer West Virginia's Democratic Sen. Joe Manchin, who is facing a tough re-election fight this year.

Trump's central message this week has focused on his efforts to beef up border security and illegal immigration.

"It's amazing what other countries put into the (immigration) system," the president said. "They don't put their good ones."

Trump touched upon some of the central themes he campaigned on during the 2016 election, reverting to old form when he tossed his "boring" prepared remarks behind him, opting instead to wing it.

The president celebrated his administration's tax plan, saying he chose to call it a "tax cut" plan since that language would resonate more with average Americans than tax reform.

Manchin struck back later in a statement, saying he would avoid the “political posturing back and forth” and blaming the tax plan Trump had traveled to the state to promote for rising insurance premiums.

Trump also hammered California, which has sued the federal government dozens of times since he took office, on issues ranging from voting rights to immigration.

"In many places, like California, the same person votes many times," he said. "They always like to say, 'Oh, that's a conspiracy theory.' Not a conspiracy theory, folks. Millions and millions of people."

Trump has not offered any evidence to support his longtime claim that millions of immigrants voted illegally in the 2016 election.

With his White House victory rarely far from his mind, Trump praised West Virginia for its support.

"I just want to congratulate the state of West Virginia because I'm so proud of you," he said of the state where he defeated Clinton by more than 40 points. "You were with me from day one. From day one."