The White House rejected Democrats request to bring senior adviser Stephen Miller before the House Oversight Committee to testify, according to a letter obtained by the Washington Post late Wednesday.

“We are pleased that the Committee is interested in obtaining information regarding border security and much needed improvements to our immigration system,” White House counsel Pat Cipollone wrote to Oversight Committee Chairman Elijah Cummings (D-MD) in the letter, but only offered to make “cabinet secretaries and other agency leaders” available to discuss policy. In his initial request Cummings asked that Miller specifically come to testify on May 1.

“It appears that you are one of the primary moving forces behind some of the most significant — and in my view, troubling — immigration policies coming out of the Trump White House,” Cummings wrote in the initial request.

Miller is believed to be the shadow figure behind President Trump’s most hardline immigration moves, especially his recent interest in making cuts to legal immigration and visa programs.