President Donald Trump has asked aides to prepare an executive action for his signature as soon as Thursday to order an investigation into voter fraud, two senior administration officials said Wednesday.

The announcement is set to follow Trump’s public call for a probe in a pair of tweets Wednesday morning, and follows the White House confirming that the president still believes, without specific evidence, that 3 to 5 million votes were cast illegally in 2016 election, depriving him of a popular vote victory.

Trump has made the claim since the election, and brought it up at a reception with congressional leadership Monday evening.

On Tuesday, White House spokesman Sean Spicer reaffirmed the president’s belief in the alleged fraud.

“He continues to maintain that belief based on studies and evidence that people have presented to him,” he said. But independent experts, congressional leaders of both parties, and Secretaries of State nationwide have affirmed there were no widespread instances of fraud in the last election.

Read More: President Trump Keeps Alleging Massive Voter Fraud. Here’s Why He’s Wrong

On Wednesday, Spicer stopped short of calling it a task force, but suggested the investigation would involve a range of people, and look beyond just the 2016 election to reviewing voter identification requirements and voter roll laws nationwide.

“Part of that is to figure out the extent of the problem,” Spicer said. “In some states, what it takes to get a driver’s license might be an issue. But I think we have to understand where the problem exists; how deep it goes; and then suggest some remedies to it.”

Trump’s electoral win bought him to the White House, but the president has repeatedly complained about losing the popular vote by nearly 2.9 million votes, or 2.1 percent of votes cast. Spicer told reporters that the investigation would be focused on the larger, Democratic-leaning states that were not electoral battlegrounds in 2016.

“A lot of these issues could have occurred in bigger states, that’s where I think we’re going to look,” Spicer said.

The officials cautioned that the Thursday signing was the president’s intended timetable, and that it could slip as the formal language of the order is still being worked on.

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