President Donald Trump is expected to announce during a nationally televised address Thursday night that at least 278,000 noncitizens are registered to vote in federal elections across the United States, according to information expected to be released by the Department of Homeland Security.

A source familiar with the matter told The Post that the figure comes from a forthcoming DHS report and represents the largest publicly disclosed number of noncitizen voter registrations ever reported in the country.

Although the total has raised significant concerns, the source said investigators have not yet determined how many of those registered individuals may have actually cast ballots illegally or what specific actions the administration intends to take in response.

The source added that the true number could ultimately be higher because the current total only reflects data collected from the states examined so far. The source declined to specify how many states have had their voter registration records reviewed.

Federal law prohibits noncitizens from voting in U.S. elections, with violations carrying penalties of up to one year in prison and financial fines. However, responsibility for confirming a person’s eligibility to vote rests primarily with individual states.

The anticipated voter registration findings are expected to be only one portion of Trump’s primetime remarks, which administration officials caution remain subject to revision before the president speaks at 9 p.m. Eastern.

“As usual, anonymous sources are speculating about what President Trump will say during his speech on Thursday evening,” White House Press Secretary Karoline Leavitt told CBS. “The truth is, nobody knows yet what President Trump will ultimately say, which is why everyone should tune in.”

Trump is also expected to use the speech to build support for the SAVE America Act, legislation that would require voters to provide proof of U.S. citizenship before casting ballots in federal elections while also implementing additional election security measures. The proposal has remained stalled in Congress despite repeated Republican efforts to advance it.

Republicans have attempted multiple times to move the legislation through the Senate, describing it as one of Trump’s highest legislative priorities this year, but Democratic filibusters have prevented the bill from moving forward.

According to the source, Trump may urge Americans to contact members of Congress and press them to approve the legislation.

The expected address follows action by the Department of Justice last week, when it sent warning letters to election officials nationwide stating they “could be criminally prosecuted for aiding noncitizen voting” if ballots cast by noncitizens are counted in an election.

Although White House officials have revealed few details about the speech, Leavitt told reporters Thursday that its central focus would be election integrity and suggested the information Trump plans to disclose “will shock you.”

“We should have the safest and most secure elections in the history of the world,” she said. “And what the president will be speaking about tonight will show you that perhaps that is not the case.”

Leavitt also maintained that safeguarding elections should not be viewed as a partisan issue, saying “the American people will be relieved to hear what they are hearing from the president of the United States” during the address.

“I think all Republicans and Democrats should recognize this should be a nonpartisan issue,” Leavitt said. “If we don’t have safe and secure elections in our country, we cannot have a country. It is a vital part of our democracy, of our constitutional republic.”

She also noted that the federal statute making it a crime for noncitizens to vote—the Illegal Immigration Reform and Immigrant Responsibility Act of 1996—was signed into law by Democratic President Bill Clinton.

The speech also comes after CBS reported Wednesday evening that Trump is expected to discuss allegations that Beijing “compromised US voter data,” along with purported “evidence the CIA knew about the action and didn’t share that information” with the president at the time.

The White House, however, appeared to push back on that report, offering CBS what was described as a tacit denial regarding those claims.