Tim Scott warns of Iranian, Afghan 'sleeper cells' in US due to border crisis

EXCLUSIVE: Sen. Tim Scott, R-S.C., issued a dire warning about the U.S. border crisis during an event at the Republican National Convention (RNC) on Wednesday.

"We have men from Yemen, Iran, Iraq, Afghanistan, Lebanon crossing…our southern border," Scott said during a South Carolina GOP delegation breakfast. "I believe we have sleeper cells in this nation as a result of Joe Biden."

"We've got to fire him," Scott added as the room applauded in response. 

BIDEN CAMPAIGN, DNC RESTART REPUBLICAN CONVENTION COUNTERPROGRAMMING AFTER TRUMP ASSASSINATION ATTEMPT

Scott's warning of terror threats at the border is not new – FBI Director Chris Wray told Congress in March that there is "no doubt" criminals have come across the southwestern border, though no specific threats were outlined. 

Wray said at the time, "There is a particular network where some of the overseas facilitators of the smuggling network have ISIS ties that we’re very concerned about, and that we’ve been spending an enormous amount of effort with our partners to investigate."

His speech comes as the RNC is expected to kick off its third day of programming, with Wednesday's theme focused on national security. 

LIVE UPDATES: REPUBLICAN NATIONAL CONVENTION

Border security is likely to be a central topic of the evening as Republicans continue to hammer the Biden administration for its handling of the migrant crisis at the southwestern border.

"How many of y'all have a back door?" Scott asked the audience. "You see, my back door is locked. Anybody disagree with that?"

Members of the crowd shouted "no" in response. 

"If you won't leave your back door unlocked at night, why would we leave the back door of the greatest nation on the planet unlocked?" Scott asked.

He continued to warn about the threat of foreign nationals from other continents, "If we, and I believe that we do, if we have a national security risk that's across our southern border, think about this…we have 100,000 Chinese nationals that have crossed our southern border."

TRUMP ANNOUNCES JD VANCE AS HIS RUNNING MATE

Law enforcement sources told Fox News on Tuesday that former President Trump's U.S. Secret Service protection was strengthened in recent weeks following intelligence about an Iranian plot to assassinate him. Iran has denied culpability.

CLICK HERE TO GET THE FOX NEWS APP

And while Republicans and some moderate Democrats have criticized the Biden administration's approach to the border crisis, Biden and his allies continue to accuse the GOP of derailing a bipartisan border security deal that Republicans said at the time did not go far enough.

A White House spokesperson referenced the bipartisan effort and the recent drop-off in illegal border crossings in a statement to Fox News Digital.

"This week, DHS announced that – after the Presidential Proclamation that President Biden announced on June 4 – the number of encounters at our Southwest Border have decreased by more than 50%. Currently, average daily encounters are lower than when President Trump left office and they are lower than at this point in 2019, before the pandemic," the spokesperson said.

"Additionally, since the Presidential Proclamation, DHS has removed and returned more than 50,000 individuals to more than 100 countries, including by operating more than 175 international repatriation flights; and DHS has doubled the percentage of noncitizens removed or returned directly from CBP custody."

"President Biden is doing his job and taking action. If Republican elected officials truly cared about fixing the broken immigration system and securing our border, they would support the bipartisan border security agreement instead of blocking it for partisan politics."

Fox News' David Spunt contributed to this report