Congressional Democrats are calling for special counsel Robert Mueller's report on the Russia investigation to be fully released, including the underlying evidence. They are threatening subpoenas if it is not.

The demands are setting up a potential tug of war between congressional Democrats and President Donald Trump's administration that federal judges might eventually have to referee.

Mueller turned over his long-awaited report to Attorney General William Barr on Friday.

The American flag flies over the White House as a helicopter practices landing on the South Lawn as vehicles move along 16th Street, in northwest Washington, Friday March 22, 2019. Special counsel Robert Mueller has concluded his investigation into Russian election interference and possible coordination with associates of President Donald Trump. The Justice Department says Mueller delivered his final report to Attorney General William Barr, who is reviewing it. Mueller's report, still confidential, sets the stage for big public fights to come. The next steps are up to Barr, to Congress and, in all likelihood, federal courts.(AP PhotoPablo Martinez Monsivais)

The American flag flies over the White House as a helicopter practices landing on the South Lawn as vehicles move along 16th Street, in northwest Washington, Friday March 22, 2019. Special counsel Robert Mueller has concluded his investigation into Russian election interference and possible coordination with associates of President Donald Trump. The Justice Department says Mueller delivered his final report to Attorney General William Barr, who is reviewing it. Mueller's report, still confidential, sets the stage for big public fights to come. The next steps are up to Barr, to Congress and, in all likelihood, federal courts.(AP PhotoPablo Martinez Monsivais)

Six Democratic House committee chairmen wrote in a letter to Barr later Friday that if Mueller has any reason to believe Trump "has engaged in criminal or other serious misconduct," the Justice Department should not conceal it.

It's unclear what Mueller has found related to the president. Barr said Mueller's conclusions could be released over the weekend.