WASHINGTON — White House adviser Stephen Miller wants to ramp up the use of Border Patrol agents as asylum screeners in an effort to curb the number of migrants who win initial entry to the U.S., according to an internal email obtained by NBC News.

In the email, a National Security Council official tells Customs and Border Protection officials to come prepared to a meeting scheduled for Friday, July 26, because Miller is interested in the rate of approval for initial screenings for migrants interviewed by Border Patrol agents versus asylum officers.

The first step for migrants seeking asylum in the U.S. is convincing asylum officers that they have a "credible fear" for their safety if they return to their home countries. The asylum officers, referred to in the email as "CIS" because they work for U.S. Citizenship and Immigration Services, were giving approval at rates above 90 percent.

"I can almost assure you," said the email, "that the credible fear integrity (discussion) will be centered on the numbers ... you all are seeing with [Border Patrol] agents assessing credible fear as opposed to the 97 + % he was seeing only with CIS."

In the same email, the National Security Council official said, "My mantra has persistently been presenting aliens with multiple unsolvable dilemmas to impact their calculus for choosing to make the arduous journey to begin with."

In May, USCIS began training 60 border agents on how to conduct the initial asylum screening, or credible fear interview, and those officers have now been dispatched to the field. At the time the Department of Homeland Security, which oversees both border agents with CBP and asylum officers with USCIS, said the move was to increase manpower for asylum screenings in response to a spike in the number of immigrants coming across the southern border.

But the emails obtained by NBC News suggest Miller and others in the Trump administration have another motive: To curb the number of immigrants passing their credible fear interview.

The official went on to say in the email quoted above that "(Miller) might press for an answer on when the (asylum) officers will no longer be looking over the shoulders of agents."

One current and one former DHS official, both speaking on the condition of anonymity, said Miller has long seen asylum officers as soft and believes border agents would be tougher critics of asylum seekers.

On average, asylum officers approve about 90 percent of credible fear screenings. The final decision on asylum for a migrant comes from an immigration judge. The administration has said that the bar for passing the initial interview is too low. In fiscal year 2018, about 65 percent of adjudicated asylum decisions ended with a denial.

A second email referenced other agenda items for Friday's meeting, including a plan to deport Central Americans from the country without a trial in the way only immigrants from contiguous countries are removed now.

Customs and Border Protection referred a request for comment to DHS. The National Security Council referred a request for comment to the White House. The White House and DHS did not immediately respond to requests for comment.