UPDATE 2-White House's Mulvaney to sue over House impeachment subpoenas

White House acting Chief of Staff Mick Mulvaney on Monday withdrew his request to join a lawsuit seeking a court ruling on whether witnesses must testify in the U.S. House of Representatives impeachment inquiry into President Donald Trump, saying he would bring his own case, according to a court document. Mulvaney earlier had sought to participate in a lawsuit filed by Charles Kupperman, a former deputy to ousted national security adviser John Bolton, seeking a court ruling on whether he should comply with a congressional subpoena or honor the Trump administration's order not to testify.

Mulvaney withdrew the request following a conference call held by the judge assigned to Kupperman's lawsuit, which was closed to media. Mulvaney said in a one-page court filing that he intended to "refile" his claims "in the matter discussed on this evening's telephonic conference, as a separate related case."

Last week, House Democrats withdrew their subpoena to Kupperman, saying they did not want to delay the impeachment investigation, and asked a judge to dismiss the litigation as moot.