The purge, they said, was the culmination of months of clashes with Mr. Miller and others around the president who have repeatedly demanded implementation of policies that were legally questionable, impractical, unethical or unreasonable. And when officials explained why, it further infuriated a White House set on making quick, sweeping changes to decades-old laws.

In a twist, many of the officials who have clashed with the White House were the president’s own political appointees, who share his broad goal of limiting immigration into the United States. To that end, they have already succeeded in lowering the number of refugees allowed into the United States, imposing a travel ban on entry from mostly Muslim nations, speeding up denaturalization proceedings, slowing asylum processing at ports of entry and developing proposals to limit work permits for spouses of high-tech workers…

Immigration officials on the conference call did not disagree that too many migrants were granted asylum in the initial “credible fear” screening. But the rules for conducting the screenings were written into law by Congress and designed to be generous so that persecuted people had a real opportunity to seek asylum. It was unclear, the officials said, what else the agency could do.

Listening to Mr. Miller continue to hammer the issue, two people on the call recalled, it was almost as if Mr. Miller wanted asylum officers to ignore the law. At one point during the call, Mr. Cissna erupted in frustration.