ISTANBUL (Reuters) - Turkey summoned a top U.S. diplomat to its foreign ministry on Sunday, a day after the U.S. Embassy’s Twitter account liked a tweet regarding Devlet Bahceli, the leader of the nationalist party who has recently fallen ill.

FILE PHOTO: A woman walks past a banner for the upcoming local elections in Ankara, Turkey, March 27, 2019. Banner with pictures of Turkish President Tayyip Erdogan and Devlet Bahceli, leader of Nationalist Movement Party (MHP), reads: "People's Alliance: The unity of common sense." REUTERS/Umit Bektas

The tweet said Turkey should be ready for a political realm without Bahceli, who has had health issues in recent weeks, which lead to speculation regarding the seriousness of his condition.

The dispute comes at a time when relations between the NATO allies are strained due to Turkey’s threats of an incursion into northeastern Syria, after Ankara accused Washington of stalling efforts to establish a ‘safe zone’ there together.

Bahceli is the leader of Nationalist Movement Party (MHP), which is an ally of President Tayyip Erdogan’s AK Party. The two parties entered the parliamentary and presidential elections in an alliance last year, which allowed them to attain a majority in parliament together.

Turkey’s Foreign Ministry said on Sunday it had summoned the U.S. Charge d’Affaires to the ministry and requested an “open and clear” explanation regarding the issue.

The U.S. Embassy posted two apologies on Twitter, one late on Saturday and another on Sunday, after the Charge d’Affaires was summoned.

The Tweet in question was sent by a user named Ergun Babahan.

“We apologize for the mistake that occurred on our Twitter account yesterday. We do not associate ourselves with Ergun Babahan nor do we endorse or agree with the content of his tweet. We reiterate our regret for this error,” it said in Sunday’s tweet. The like was also removed from the Embassy’s page.

Omer Celik, spokesman for the AK Party, said earlier on Sunday that the U.S. 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,” Celik said on Twitter.

“The United States Embassy needs to try to understand Turkey not through people linked with terrorist organizations but through people who can conduct proper analysis,” he said.

Turkey has placed on trial on terrorism charges three local U.S. consulate employees. One of them was sentenced to jail in January but was released due to time served. The trials of the other two, who are accused of links to Gulen’s network, are continuing.

Semih Yalcin, deputy head of the MHP, said on Twitter late on Saturday that Bahceli has recovered from his illness and would return to work in the coming week.

The relations between the NATO allies have been under pressure in recent years over a range of issues, including Turkey’s purchase of Russian S-400 missile defense systems, differences in policy in Syria and the detention of local U.S. consulate employees and citizens in Turkey.