Turkey on Sunday summoned the US charge d'affaires after the embassy's Twitter account 'liked' a tweet about a nationalist politician who was recently in hospital, the Turkish foreign ministry said.
"Today the US charge d'affaires was summoned to the ministry to give an open and clear explanation of the social media posting," the ministry said.
It added that the United States' ambassador was not in Ankara on Sunday.
The embassy's official Twitter account had liked a tweet on Saturday in which an individual said Turkey should be ready for a political period without Devlet Bahceli.
Bahceli leads the Nationalist Movement Party (MHP), the junior partner of President Recep Tayyip Erdogan's ruling Justice and Development Party (AKP) since their formal alliance in 2018.
The MHP also backed the AKP in a 2017 referendum on changing the Turkish constitution to transform the country's system into an executive presidency.
Last month Bahceli, 71, was taken to hospital after suffering nausea but was released shortly after. Despite assurances, there have been concerns recently over his health.
The US ambassador, David Satterfield, arrived in Turkey earlier this year after a period of nearly two years without an American ambassador to Ankara following John Bass' departure in 2017.
The US embassy late on Saturday apologised in a tweet, saying the posting had been "liked by accident".
Relations between Turkey and the United States have been strained in recent years over multiple issues including US support for a Syrian Kurdish militia viewed by Ankara as terrorists.
Erdogan on Saturday renewed his threat to launch an air and ground operation against the Kurdish militia in northeastern Syria despite US opposition.
Turkish and American officials in August agreed a deal to set up a buffer zone on Turkey's border, and Turkey has been pushing for a "safe zone" but has accused the US of stalling over its establishment.