Former Homeland Security Secretary Jeh Johnson on Thursday credited President Trump with sharply reducing illegal immigration through the southwestern U.S. border just through the power of his tough talk against illegal migrants.

"Illegal migration on our southern border has gone down since this president has been in office, basically because, through his rhetoric, he scared off a lot of women and children in Central America who'd rather stay in their desperate circumstances, or just migrate to Mexico and stop there," Johnson said.

While working for former President Barack Obama, Johnson and other officials worked for years to reduce illegal immigration after the 2014 border crisis that saw thousands of unaccompanied children try to enter the country. Illegal immigration fell in 2015 after the Obama administration worked closely with Central American countries in an effort to get their help in reducing the flow of people, but it rose again in 2016, Obama's last full year in office.

Under Trump, the flow of illegal immigrants fell immediately, which most chalked up to Trump's tougher policy position on immigration, which included new direction to DHS that said agents need to look to deport anyone who enters illegally.

Johnson said under Obama, officials looked to deport only the most dangerous immigrants. But Johnson said he believes Obama's policy was "humane," and said he hoped the Trump administration would approach the problem the same way.

"I believe that we have to enforce our immigration laws consistent with our values and consistent with humanity," he said.

"At the end of the day, when you enforce immigration laws, you have to be able to look at yourself in the mirror, look your own family in the eye, recall the women and children who are desperate, to say, 'I did my best to enforce the law consistent with our priorities and consistent with our values,'" he said. "I hope that the current administration does not lose sight of that."