New York City Mayor Bill de Blasio, widely known to have been pondering a White House run, is expected to announce his official entry into the crowded candidate field on Thursday, a source familiar with the situation told Fox News on Wednesday.

De Blasio will make the announcement in a Thursday morning video followed by an appearance on ABC News' "Good Morning America," said the source, who requested anonymity.

The mayor would be the 23rd Democrat vying for the Democratic presidential nomination, following Montana Gov. Steve Bullock, who announced his own candidacy on Tuesday.

De Blasio has plans to visit a pair of early-voting states. He will travel to Iowa on Friday and South Carolina on Saturday, a spokesperson told Fox News.

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The mayor has been teasing an announcement this week about his decision.

And he's made several campaign-style trips to states expected to play key roles in the Democratic nominating process.

Most recently, in the lobby of Trump Tower in New York City on Monday, de Blasio faced a crowd of protesters at a raucous rally promoting the city’s Green New Deal. A press conference appeared to be laying the groundwork for his candidacy announcement.

Speaking in front of the same escalators where Trump launched his 2016 campaign, the Democrat threatened Trump’s family company with millions of dollars in fines if his buildings don’t comply with new environmental standards.

“His buildings are one of the biggest polluters in New York City,” de Blasio said, blasting the president's rollback of Obama-era environmental policies, his move to pull the United States out of the Paris climate accord, and his appointment of climate change skeptics to the Cabinet.

“Cut your emissions or we’ll cut something you really care about,” de Blasio said. “We’ll take your money.”

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The attention-grabbing location attracted Trump supporters, who heckled the mayor as he struggled to make himself heard.

After the news conference, de Blasio and the president’s son, Eric Trump, had an exchange on Twitter.

Eric Trump blasted the Democratic mayor for attacking the Trump Organization, calling it an unethical "abuse of power." He boasted of the "thousands" of New Yorkers his family business employs.

De Blasio’s potential candidacy has generated little enthusiasm from hometown constituents so far.

A recent Quinnipiac University poll found 76 percent of New York City voters said they believed de Blasio shouldn’t run and gave the mayor “an anemic 42-44 percent job approval rating.”

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At the same time, newspapers have poked fun at de Blasio’s presidential ambitions, noting that while he won two mayoral elections by large margins and can point to real achievements, including expanding free public prekindergarten citywide, he has also developed a reputation among some critics for being politically ineffective.

Fox News' Tamara Gitt, Paul Steinhauser and The Associated Press contributed to this report.