Four-in-five asylum seekers at the southwest border do not meet the criteria to enter the United States, according to Homeland Security Secretary Kirstjen Nielsen.

"The way the system works right now the threshold under law is so low that about 80 percent pass that initial interview, but only 20 percent are granted asylum by a judge, which tells us that 80 percent of that is either just a flat-out fraud or somebody who thinks they can come here because they want a job here. That's not asylum. Or 'I want to reunify with my family.' That's not asylum. 'I just want to come to the United States' — not asylum. We have legal ways to do that, but it's not through asylum," Nielsen told Fox News host Laura Ingraham.

Nielsen said a significant uptick in apprehensions of illegal immigrants at the U.S.-Mexico border in March and April are due to "loopholes" in immigration law that migrants have learned how to use to game the system.

Attorney General Jeff Sessions announced in early May that he had instructed the Executive Office of Immigration Review and DHS' U.S. Citizenship and Immigration Services to prosecute all illegal entrants instead of only the most serious violators. Sessions said he wanted to send a message to people attempting to claim credible fear that the U.S. would punish anyone who knowingly lied in order to enter the country.

Nielsen said U.S. Customs and Border Protection officers and Border Patrol agents have learned why many travel to the U.S., often through Mexico to get to America.

"They know if they cross between the ports of entry that nothing will happen. If they bring kids, they will be released. The kids will be released in 20 days under a court case. If they are criminal, they will serve a little bit of time and under a different court case they have to release them in six months back to the communities," Nielsen said. "If they're other than Mexican, we can't put them in expedited removal if there are children involved."