(CNN) The White House has informed the House Oversight Committee that aide Stephen Miller will not testify before the panel about his role in President Donald Trump's controversial immigration policies, according to a letter obtained by CNN.

In the Wednesday letter , White House counsel Pat Cipollone says there's "long-standing precedent" for the White House to decline offers for staff to testify on Capitol Hill. Instead, the White House counsel said Cabinet secretaries and other executive branch officials would make a "reasonable accommodation" for House Oversight Chairman Elijah Cummings' questions on immigration policy.

But the move is likely only to ratchet up tensions between the White House and the Maryland Democrat after both the administration and the Trump Organization have defied three of his subpoenas this week alone -- and have pushed back against a number of his other demands.

Miller, an immigration hard-liner, has been one of the more influential voices in the White House and was seen as a driving force behind several of Trump's immigration policies, including the President's recent idea to send detained migrants to sanctuary cities largely run by Democrats.

Last year, Miller advocated for the Trump administration's "zero tolerance" policy for people illegally crossing the border into the US, which resulted in children being separated from their parents at the border, and he's been a consistent advocate of the hard-line immigration policies that have been a centerpiece of Trump's domestic agenda.

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