WASHINGTON (Reuters) – The Trump administration has barred U.S. congressional travel on government-owned or operated aircraft during the partial government shutdown, unless they have White House approval, according to a memo issued on Friday by the White House Office of Management and Budget.

The move marks an escalation by the White House, which on Thursday blocked U.S. House Speaker Nancy Pelosi from using a military plane for a congressional trip to Afghanistan. Pelosi’s office accused the administration of leaking commercial travel plans on Friday, which a White House official has denied.