With thousands of asylum-seeking migrants making their way toward the U.S.-Mexico border, the Trump administration is looking at options to restrict or block outright their ability to enter the country.

Officials said everything is on the table with respect to sealing the border, including denial of asylum applications based on the so-called "travel ban" of 2017.

No final decisions have been made, they said, because some of the more aggressive proposals will invite legal challenges.

Officials are looking overall at ways to crack down on border crossings – including migrants who are part of the caravan that left Honduras on Oct. 12 and are more than 1,000 miles from the U.S. border.

“The administration is considering a wide range of administrative, legal and legislative options to address the Democrat-created crisis of mass illegal immigration," a White House official said. "No decisions have been made at this time. Nor will we forecast to smugglers or caravans what precise strategies will or will not be deployed.”

More:President Trump latches onto migrant caravan as top issue in midterms

Part of that overall plan involves manpower: The Pentagon is preparing to deploy at least 800 troops to the border.

Trump also has pledged to seal the border if necessary.

Though the current migrant caravan is more than 1,000 miles from the border and traveling by foot, Trump has increasingly seized on the caravan as an issue in the midterm elections, hoping the images of migrants walking through Mexico will energize voters.

Federal officials have in the past found that many of the migrants are entitled to an asylum review. Of 401 members of another caravan requesting asylum this year, 374 passed the first test, demonstrating that they have a “credible fear” of returning to their home country.

Department of Homeland Security Department Secretary Kirstjen Nielsen said Thursday night that the Trump administration is considering all options to deal with the migrant caravan.

“Everything is on the table,” Nielsen told Fox News in an interview from Yuma, Arizona.

"If they come here illegally with no legitimate reason to stay, they absolutely will be apprehended and removed immediately," she said.

"They should be seeking refuge in Mexico," said Nielsen. "To ignore, basically, refuge and continue, in some cases, to come to the United States raises questions of what their real motives are."

"This caravan cannot come to the United States. They will not be allowed in. They will not be allowed to stay."

Human Rights First, a non-profit and non-partisan rights group, spoke out against this proposed regulation, saying President Trump is "misinterpreting the law."

"The fact that the president can apply it to asylum is where we say no," Jennifer Quigley said.

She's an advocacy strategist for refugee protections with Human Rights First who says she's familiar with the proposed regulation.

Quigley said such a move from the Trump administration would be a violation of the U.S. Constitution's due process clause and obligations under international law, such as the Refugee Convention.

The restrictions under consideration recall Trump's travel-ban efforts early in his presidency against predominantly Muslim countries. This summer, a deeply divided U.S. Supreme Court upheld the ban as a legitimate exercise of executive branch authority.

At the time of the court's ruling, Trump said:

"In this era of worldwide terrorism and extremist movements bent on harming innocent civilians, we must properly vet those coming into our country. This ruling is also a moment of profound vindication following months of hysterical commentary from the media and Democratic politicians who refuse to do what it takes to secure our border and our country."

Contributing: Rafael Carranza, The Arizona Republic.