One of President Donald Trump's fiercest allies in his administration faces a crossroads after he was forced to backpedal on a key issue, according to a new report.

The New York Times reported on Sunday that Stephen Miller, Trump's deputy chief of staff for policy, is facing questions about how he can continue to drive the Trump administration's hard-line approach to enforcing immigration law, given the waning appetite of the Republican Party and the American public over the brutal images of immigrants being forcibly detained by federal agents.

Miller has been a key architect of the Trump administration's immigration policies, and at one time seemed to be telling federal agents to "Push the limits" when it comes to the tactics they use to deport people, according to the report.

"Eight months later, Mr. Miller did something startling — he backpedaled," the report added.

"Now, Mr. Miller, 40, one of the most influential presidential advisers in recent memory and an unabashed champion of Mr. Trump’s hard-line immigrant crackdown, is at a crossroads," it continued. "He faces questions about how aggressively he can continue to drive the deportation campaign, and how much appetite his party and the country have for tactics that proved successful in helping to boost arrests of immigrants but reignited a polarizing debate over what it means to be American."