Ankara summoned the US charge d’affaires on Sunday after a Twitter account belonging to the country's embassy liked a tweet that suggested the leader of Turkey's nationalist party could die soon.
The Foreign Ministry said Jeffrey Hovenier was summoned despite an embassy statement that said its Twitter account had liked “an unrelated post in error”, and apologised.
Many interpreted the tweet as suggesting that the nationalist leader Devlet Bahceli could soon die.
It was posted by a journalist Turkey accuses of having links to a network led by Fethullah Gulen, a cleric who is blamed for a failed coup attempt in 2016. The journalist, Ergun Babahan, is wanted in Turkey.
The tweet drew anger from the parties of President Recep Tayyip Erdogan and Mr Bahceli, which are allies.
The main opposition party also said it regarded the embassy’s move as an insult to Turkey’s Parliament.
The embassy issued a second apology after Mr Hovenier was called to the Turkish Foreign Ministry.
“We do not associate ourselves with Ergun Babahan nor do we endorse or agree with the content of his tweet,” the embassy’s second apology read. “We reiterate our regret for this error.”
Omer Celik, spokesman for Mr Erdogan's AK Party, said earlier on Sunday that the US State Department and embassy needed to investigate the issue and an apology would not suffice.
“It shows that some people employed in the embassy are making a special effort to damage the relations between the two countries,” Mr Celik said on Twitter.
“The US embassy needs to try to understand Turkey, not through people linked with terrorist organisations but through people who can conduct proper analysis."
Semih Yalcin, deputy head of the MHP, said on Twitter late on Saturday that Mr Bahceli has recovered from his illness and would return to work in the coming week.
The incident occurred at a time when ties between Turkey and the US are strained over Syria policies.
Turkey is accusing Washington of not acting fast enough in creating a "safe zone" in north-east Syria, which would keep US-backed Syrian Kurdish fighters away from the Turkish border. Disagreements remain on the size of the zone.
Mr Erdogan has threatened intervention to drive away the Kurdish fighters.