President Trump says the number of military troops deployed to the U.S.-Mexican border could go as high as 15,000.

Mr. Trump told reporters outside the White House on Wednesday that "we'll go up to anywhere between 10 and 15,000 military personnel — on top of Border Patrol, ICE and everybody else at the border."

The president said the move would be aimed at preventing the entry of a caravan of migrants traveling from Central America. The caravan is still nearly 1,000 miles from the border, but Mr. Trump said they will be here soon. The president has doubled down on stopping the caravan at the southern border, and repeated his threat on Wednesday to stop aid to any Central American countries that let the caravan through. Mr. Trump said the U.S. is "going to be prepared" and that the migrants are "not coming into our country."

Get Breaking News Delivered to Your Inbox

Currently, there are 2,100 National Guard helping at the border. The Pentagon says an additional 5,200 active-duty troops could join them.

The president denied the idea that he's perpetuating fear ahead of the midterms with his rhetoric on the caravan and illegal immigration.

"No, not fear mongering at all. Immigration is an important subject," he told reporters Wednesday. "The Democrats have let immigration in our country get out of control with their horrible not allowing us to have any votes to get passage. We need Democrat votes to change the immigration laws. They haven't given us any votes and I actually think that they will."

The president also defended his announcement that he intends to end birthright citizenship through executive order, repeating that he believes he has the right to do so, pointing to former President Obama's move to establish the Deferred Action for Childhood Arrivals program (DACA) through executive order. In the past, Mr. Trump has suggested Obama had no right to establish DACA. Mr. Trump moved to end the DACA program last year, although that's been held up in the courts.

"I really believe we can do it through executive order," Mr. Trump said Wednesday. "One other thing, if President Obama can get DACA approved - if you look at DACA, where he actually said 'well this isn't legal this I can't do, but I'll do it anyway' and then he gets a judge to approve it, and it'll ultimately be decided by the Supreme Court I hope quickly. But certainly if he can do DACA we can do this by executive order. With that being said, I think Congress will ultimately act."

Mr. Trump said he prefers congressional action to an executive order because that's more permanent.