The White House tried to limit ex-Russia adviser Fiona Hill’s testimony to House investigators by claiming some topics could be subject to executive privilege, according to letters obtained by NBC News.

The letters between the White House and Hill’s lawyers show that the White House had tried to keep the former adviser from testifying on “direct communications with the president, diplomatic communications, meetings with other heads of state and staffing the president had on calls with foreign heads of state,” in NBC News’ words.

The White House claimed those four topics could fall under executive privilege and were therefore off-limits.

When Hill’s lawyers pushed back, White House Deputy Counsel Michael Purpura replied, “As the White House Counsel has explained, there is no valid impeachment inquiry underway.”

Though the White House did not bar Hill from testifying in the impeachment inquiry, its lawyers told Hill’s attorneys Hill “is not authorized to reveal or release any classified information or any information subject to executive privilege.”