Donald Trump speaks on the phone during a visit to a call center before the start of a rally in September. (Evan Vucci/AP)

On his popular Sunday night program “Periodismo para Todos” (Journalism for All), the muckraking Argentine reporter Jorge Lanata and his guests delivered an explosive claim: U.S. President-elect Donald Trump asked the country’s leader for help getting permits for a stalled Trump tower project in Buenos Aires.

The story spread wildly across social media Monday morning, especially in the United States, as it played into worries that the new U.S. president will use the Oval Office like an advertising agency for the Trump global brand.

That Trump would use a congratulatory call from the Argentine president, Mauricio Macri, to promote his personal business interests in such a tawdry, crass way seemed to confirm the worst fears of his critics about the potential abuse of executive power.

But the Trump-favor-seeking story may end up fitting better into another narrative of post-election U.S. politics: the easy spread of thinly sourced or even fake news.

Ivan Pavlovsky, a spokesman for Macri who was present in the room during their call, said the claims were false and that “nothing like that ever happened.”

“They didn’t talk about any investments or any tower,” said Pavlovsky, reached by phone in Buenos Aires. “They talked about good relations between Argentina and the United States and the time they first met each other, more than 20 years ago” in New York City, said Pavlovsky.

Trump transition spokesman Jason Miller also denied the report in an email to USA Today.

The allegation that caught fire on social media Monday started on the previous evening’s broadcast of “Journalism for All.”

Lanata, best known in Argentina as a fierce and irreverent critic of former president Cristina Fernández de Kirchner, said during the show’s opening monologue that he had a story about Trump that was “half joking, half serious.”

“Macri called him,” Lanata told his audience. “Trump asked him to approve a tower he’s building in Buenos Aires. It wasn’t only a conversation about geopolitics.”

It wasn’t clear whether Lanata meant the allegations were “half serious” or whether the story so defied credulity as to seem like a joke. Nor did he reveal the sources for his claim.

During the segment about the alleged conversation, one of Lanata’s guests, journalist Romina Manguel, said Trump had, years earlier, joined a group of investors who had purchased a parking garage with the intention of building a tower.

The $100 million project was held up by red tape and currency controls imposed by then-president Kirchner, a leftist, and the permits for the 35-story tower had since expired, according to Argentina’s La Nacion.

Pavlovsky adamantly denied that the project came up during the brief conversation between Trump and Macri. “They talked about maintaining good relations between the two countries,” he said.

While officials denied any impropriety, one unusual aspect of the call was confirmed: Trump's daughter Ivanka joined the conversation with the Argentine leader. Macri told a Japanese newspaper reporter in an interview published Monday that he had met Donald Trump years earlier, when the politicians were both businessmen. “In the call [on Nov. 14], I also talked with his daughter,” Macri said, according to the newspaper Asahi Shimbun. “I have known her since her infant days.” He did not provide details.

Ivanka Trump stirred an outcry by attending her father's meeting with Japanese Prime Minister Shinzo Abe last Thursday. Ivanka and her two brothers are planning to run their father's businesses while he is in the White House, an arrangement that has been criticized for potential conflicts of interest.

Donald Trump has a lot of potential conflicts of interest as president – but there's no law that specifically requires a commander in chief to remove themselves from all of their business interests. The Fix's Peter W. Stevenson explains why presidents usually put their assets in a "blind trust" to avoid problems. (Peter Stevenson/The Washington Post)