WASHINGTON — President Donald Trump said Wednesday that the number of military troops deployed to the U.S.-Mexican border could go as high as 15,000 as he draws a hard line on immigration in the lead-up to the midterm elections.

With his eyes squarely on next Tuesday’s contests, Trump has rushed a series of immigration declarations, promises and actions as he tries to mobilize supporters to retain Republican control of Congress. His own Republican campaign in 2016 concentrated on border fears, and that’s his focus in the final week of the midterm fight.

“As far as the caravan is concerned, our military is out,” Trump said Wednesday. “We have about 5,800. We’ll go up to anywhere between 10,000 and 15,000 military personnel on top of Border Patrol, ICE and everybody else at the border.”

Trump rejected the idea he was “fearmongering” or using the issue for political purposes, but his escalating rhetoric in the waning days of the campaign season call into question the denial. Trump has railed against illegal immigration, including several caravans of migrants from Central America slowly moving toward the U.S. border. The caravan is still nearly 1,000 miles from the border.

He’s also promised to end so-called catch-and-release policies by erecting tent cities to hold those crossing illegally. And this week he is asserting he could act by executive order to unilaterally end birthright citizenship for the children of non-U.S. citizens.

Trump’s comments on Wednesday appeared to catch the Pentagon off guard.

The Pentagon on Monday directed 5,239 active-duty troops to deploy to the border to assist Customs and Border Protection agents in Texas, Arizona and California. That is in addition to 2,092 National Guard troops who have been along the border for several months on a separate, but related, mission.

On Tuesday, Air Force Gen. Terrence O’Shaughnessy, commander of U.S. Northern Command, which is supervising the new troop operation, disputed a news report that the active-duty total could reach 14,000.

“I honestly don’t even know where that came from,” he said. “That is not in line with what we’ve been planning.”

O’Shaughnessy said the 5,239 number will increase, but he would not say by how much or when. Other officials have said that 2,000 to 3,000 additional active-duty troops are on standby for possible deployment to the border.

A deployment of 15,000 would bring the military commitment on the border to roughly the same level as in war-torn Afghanistan.

Trump on Wednesday did not back down from his controversial proposal to upend the very concept of American citizenship. In a morning tweet, he said the right to citizenship for babies born to non citizens on American soil “will be ended one way or the other.”

He also claimed that what he terms “so-called Birthright Citizenship” is “not covered by the 14th Amendment.”

However, the text of the amendment’s opening Citizenship Cause is this: “All persons born or naturalized in the United States and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside.” The citizenship proposal would inevitably spark a long-shot legal battle over whether the president can alter the long-accepted understanding that the 14th Amendment grants citizenship to any child born on U.S. soil, regardless of his parents’ immigration status.

Speaker of the House Paul Ryan asserted Tuesday that “obviously” Trump could not upend that policy by executive order, drawing a tweeted rebuke from Trump. He said Wednesday that Ryan “should be focusing on holding the Majority rather than giving his opinions on Birthright Citizenship, something he knows nothing about!”

Speaking to reporters before leaving the White House for a campaign rally in Florida, Trump compared his plan to act by executive order to President Barack Obama’s much-maligned decision to use executive action to provide protections from prosecution and a path to work status for some people brought to the U.S. illegally as children.

“If he can do DACA, we can do this by executive order,” Trump said, using the acronym for the Obama-era Deferred Action for Childhood Arrivals program. Trump and his Justice Department have argued that Obama action was unlawful.

Trump and many top aides have long seen the immigration issue as the most effective rallying cry for his base of supporters. The president had been expected to announce new actions at the border on Tuesday, but that was scrapped so he could travel instead to Pittsburgh, where 11 people were massacred in a synagogue during Sabbath services.