Frustrated by opposition on some college campuses to conservative speakers, President Donald Trump on Thursday signed an executive order which threatens to take away federal research grant money from colleges and universities, if those schools don't guarantee First Amendment protections for those who want to speak on campus.

"We're dealing with billions and billions and billions of dollars," President Trump said in a White House ceremony on Thursday.

Flanked by conservative activists who have run afoul of protests at college and university campuses, Mr. Trump made clear that he wants new opportunities for their voices to be heard.

"Universities that want taxpayer dollars should promote free speech," the President added.

"This order is part of the Trump Administration’s administrative and legislative efforts to support a focus on student outcomes and improve transparency, accountability, and affordability in postsecondary education," the White House said in a statement.

The President had raised this matter earlier in the month, during an appearance at the Conservative Political Action Conference just outside Washington, D.C.

It was not immediately clear how the Thursday signing would change the current landscape governing money being sent to schools by the feds, as there are already requirements to uphold the First Amendment.

In a morning conference call with reporters, a senior administration official refused to give any hints about how the requirement would be enforced differently going forward.

"I won't get into implementation details," the official said, repeatedly deflecting questions in a Thursday conference call with reporters about how the plan would work.

"But schools are already supposed to be following these rules," as the official said "the goal of the order is to promote free speech more broadly across college campuses."

The plan drew immediate fire from the President's critics.

"President Trump’s concept of free speech is speech that he agrees with, which is, in fact, the antithesis of what the First Amendment seeks to protect," said Randi Weingarten, the President of the American Federation of Teachers union.