Sen. Lindsey Graham, R-S.C. warned on "Hannity" Tuesday that President Biden's immigration policies could have major national security implications, suggesting that a porous southern border might serve as a "great way for terrorists to come into our country."

Graham blamed Biden's rollback of Trump's "Remain in Mexico" policy for the recent surge of migrants at the U.S.-Mexico frontier.

"Word is out that the Trump policies are being replaced by the Biden administration [policy] that if you get one foot in America, you are never going to leave," Graham said.

"People will be coming ... by the hundreds of thousands by the summer. It is a humanitarian crisis. It’s going to be an economic crisis for our cities along the border, and eventually is going to be a national security crisis, because they’re children today but they could easily be terrorists tomorrow," he argued.

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As the country approaches the 20th anniversary of the Sept. 11, 2011 terrorist attacks, Graham warned: "Al Qaeda and ISIS would love nothing more than to hit us again ... to show that they are still alive and well ... This border insecurity is a great way for terrorists to come into our country."

The White House has been reluctant to label the situation at the border as a "crisis," but Graham warned that unless Biden implements aggressive changes and acknowledges the critical nature of the situation, the "worst is yet to come."

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"By the late spring, early summer, you are going to have families coming in caravans because the word is out in Central America they are changing the policy that Trump put in place, that if you get to the border [and] you turn yourself in, you are going to stay in America, not Mexico," he said.

"Until they reverse that policy,  until they go back to their remain in Mexico policy, the worst is yet to come."