Washington (CNN) Senate Minority Leader Chuck Schumer said Sunday that Democrats could tie a measure to protect special counsel Robert Mueller to must-pass legislation should acting Attorney General Matt Whitaker not recuse himself from oversight of Mueller's Russia probe.

"We Democrats, House and Senate, will attempt to add to must-pass legislation, in this case the spending bill, legislation that would prevent Mr. Whitaker from interfering with the Mueller investigation" should Whitaker not recuse, Schumer told CNN's Jake Tapper on CNN's "State of the Union."

Schumer's comments came as he announced that he and House Minority Leader Nancy Pelosi, along with other key Democrats, were sending a letter to Lee Lofthus, the top ethics officer at the Justice Department, asking for Lofthus to let them know if he had advised Whitaker to recuse himself from oversight of the Mueller investigation.

Schumer said Whitaker's appointment "should concern every American" and warned of a crisis should Whitaker not step aside from the special counsel investigation.

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