An article published Tuesday on the website of Foreign Policy magazine quoted an unnamed former U.S. government official as saying Zardari was "incoherent" when he spoke with President Barack Obama by telephone over the weekend.
Parts of the U.S. government were also informed that Zardari had a "minor heart attack" on Monday night and might resign on account of "ill health" amid the uproar over the memo scandal, the source said.
"The noose was getting tighter -- it was only a matter of time," the former official reportedly told Foreign Policy.
The story quickly spread on Twitter and it was picked up by Pakistan's ratings-hungry television channels.
Rumors also circulated on Twitter of an army takeover on Tuesday night, but that was quickly recanted by the original poster.
"Some elements blew up this to create unrest in the country," said Fauzia Wahab, a senior member of Zardari's Pakistan People's Party. "His visit to Dubai and having a medical check-up is perfectly normal."