House Speaker Nancy Pelosi warned that the Trump administration's defiance of subpoenas could be an impeachable offense, even as the top White House lawyer instructed his predecessor not to comply with a subpoena from House Democrats.

White House Counsel Pat Cipollone said in a letter Tuesday to the House Judiciary Committee that President Donald Trump may want to assert executive privilege over the documents the panel is seeking from former counsel Don McGahn.

At the same time, Trump's Justice Department is pushing back against a separate subpoena from the House Judiciary Committee for the full, unredacted version of special counsel Robert Mueller's report.