President Trump urged Attorney General Jeff Sessions on Wednesday to end the special counsel’s investigation into Russian interference in the 2016 election, raising more questions about whether Mr. Trump has tried to obstruct the investigation.

The White House and the president’s lawyers sought to minimize any damage by arguing that the call, issued on Twitter, was an angry opinion, not an order. Mr. Trump has also sought an interview with the special counsel, Robert S. Mueller III, and his office, in an attempt to clear himself of any wrongdoing.

Yet even as Mr. Trump characterizes the investigation as a “Russian hoax,” top administration officials came forward on Thursday to assert that Russian election interference was a serious threat and to vow to prevent it.