Ankara has vowed to retaliate against extraordinary US sanctions targeting Turkey’s interior and justice ministers over the continued detention of an American pastor, a move that has sent the lira tumbling to historic lows and threatens the longstanding alliance between two Nato allies.

The US Treasury Department said late on Wednesday it was designating Süleyman Soylu and Abdulhamit Gül, the ministers of interior and justice, as leaders of organisations that had perpetrated serious human rights violations, in response to the arrest and incarceration of pastor Andrew Brunson.

The American clergyman – who has been imprisoned for 600 days – has led a congregation in Turkey for years. He was arrested and put on trial over allegations of espionage for a Kurdish separatist group that has waged an insurgency against the state. He is also alleged to have spied for the movement of Fethullah Gülen, the exiled preacher accused of masterminding a coup attempt in July 2016. US officials say the charges are frivolous.

“Pastor Brunson’s unjust detention and continued prosecution by Turkish officials is simply unacceptable,” said the US treasury secretary, Steven Mnuchin. “President Trump has made it abundantly clear that the United States expects Turkey to release him immediately.”

The Turkish foreign ministry said Washington’s move “neither complies with state seriousness, nor is it explicable within the terms of law and justice” and vowed an “equivalent response” to what it described as an aggressive attitude from the US.

“There is no doubt that the decision, which disrespectfully intervenes with our judicial system, stands in contrast to the essence of our relations and will seriously damage the constructive efforts made in order to resolve problems between the two countries,” the statement said.

The American decision was an extraordinary rebuke to a Nato ally, highlighting the deterioration in links between the US and Turkey. That relationship has been under duress over divergent policies in Syria, the ongoing trial involving executives at a Turkish state-owned bank who allegedly helped Iran circumvent US sanctions, Washington’s delays in extraditing Gülen, and the ongoing detention of American citizens in Turkey. A brawl last year in Washington involving President Recep Tayyip Erdoğan’s security guards, who beat up protesters near the American embassy, seemed to encapsulate the broader dispute between the two countries. Senator John McCain at the time urged the expulsion of the Turkish ambassador, but assault charges against the bodyguards were later dropped.

The US president, Donald Trump, and vice-president, Mike Pence, threatened sanctions against Turkey in July after a court hearing in which Brunson was expected to be released resulted in him being placed under house arrest. Turkish officials said they would not respond to threats, and pro-government media outlets interpreted the US outburst as a move meant to placate evangelical voters ahead of midterm elections later this year.

Turkey has repeatedly said it would not interfere with the rule of law in the Brunson case, even though Erdoğan hinted in a speech earlier this year that the authorities could turn over the American pastor if Gülen was extradited to Turkey. US media had reported that Brunson was to be released as part of a deal that involved the release of Ebru Özkan, a Turkish citizen who had been imprisoned in Israel, and in exchange for leniency in the Iran sanctions case.

Turkish officials have repeatedly denied the existence of such a deal.

Gül and Soylu have dismissed the sanctions against them and said they did not own property in the US. But the Turkish lira, already under strain over the government’s economic policies, crossed the threshold of 5TL to the US dollar, a historic low.