McDonald's says it has been notified by Twitter that its account was "compromised" after it appeared to send a message calling Donald Trump "a disgusting excuse of a President".
The tweet to Mr Trump from the official account for McDonald's, a message that has since been deleted but was captured in a screenshot, said it would love to have President Obama back. "Also you have tiny hands," the tweet told Trump.
The tweet was also temporarily pinned to the top of the McDonald's account so that it would be the top message people see if they visited the company's Twitter profile.
"Twitter notified us that our account was compromised. We deleted the tweet, secured our account and are now investigating this," McDonald's spokeswoman Terri Hickey said in a statement.
Mr Trump did not respond to McDonald's on Twitter.
The tweet caused a sensation in Twitter, where users shared copies of the deleted tweet and offered jokes and comments.
Vanessa Veasley and other users speculated that Trump supporters could launch a boycott of the chain, as they threatened to do after Starbucks Corp chief executive Howard Schultz vowed to hire 10,000 refugees after Trump's first executive order temporarily banning refugees from certain countries.
"McDonald's already deleted the tweet? lol Well at least Trump supporters can finally boycott something they can actually afford," @VanessaVeasley wrote.
Other users praised the fast-food chain, which has been fighting to reverse two straight years of customer traffic declines.
"Suddenly I want a Big Mac, well done @McDonalds," tweeted Shay Steward Bouley (@blackgirlinmain).
Mr Trump, one of the more fast-food friendly Presidents in recent history, tweeted pictures of himself eating fast food during the US election campaign. A 2002 McDonald's ad featured Mr Trump and the chain's Grimace mascot promoting McDonald's since-discontinued Big N' Tasty burger for US$1.