Former CNN host Soledad O'Brien on Sunday went after Sen. Tom Cotton (R-Ark.) for a tweet he made regarding migrants seeking asylum.

Cotton tweeted on Friday that he applauded "the administration's efforts to fix our broken asylum system."

O'Brien shot back, calling Cotton "ignorant."

"Senator Cotton is remarkably ignorant (and it's probably intentional) of the law as it applies to asylum claims," O'Brien, a frequent critic of the Republican Party, tweeted Sunday.

"They must present themselves at a border. That's the policy."

"I applaud the administration's efforts to fix our broken asylum system," Cotton wrote Friday. "Individuals with valid asylum claims should apply in their home countries or a safe third country, not by showing up at our border."

"We will not let anyone take advantage of America's generosity by exploiting loopholes in our immigration system," he continued, in another tweet. "Congress should also act to codify these common-sense reforms."

People may only apply for asylum at the U.S. border or from within the country, according to U.S. Citizenship and Immigration Services.

The Hill could not reach Cotton's office for immediate comment.

On Friday, President Trump signed a proclamation blocking asylum claims from immigrants who enter the U.S. illegally.

"We want people to come into our country, but they have to come into the country legally," Trump told reporters.

Asylum has become a larger issue in national discourse as a caravan of nearly 4,000 migrants makes its way toward the U.S. border.

The caravan left Mexico City on Saturday and is heading towards the U.S. southern border, Fox News reports.

The White House has ordered over 5,000 troops to the border to brace for the caravan, which Trump has called an "invasion."