U.S. President Donald Trump said he’ll impose “large sanctions” on Turkey over the detention of an American pastor, plunging relations between the two NATO allies to a new low and extending a rout on Turkish financial markets.

Andrew Brunson, an evangelical minister detained on charges of involvement in a failed 2016 coup in Turkey, is “a great Christian, family man and wonderful human being,” Trump said in a tweet Thursday. “He is suffering greatly. This innocent man of faith should be released immediately!”

Donald J. Trump@realDonaldTrumpThe United States will impose large sanctions on Turkey for their long time detainment of Pastor Andrew Brunson, a great Christian, family man and wonderful human being. He is suffering greatly. This innocent man of faith should be released immediately!

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Turkey’s Foreign Minister Mevlut Cavusoglu responded on Twitter, saying that the country “will never tolerate threats from anyone.” Ibrahim Kalin, a spokesman for President Recep Tayyip Erdogan, said the use of “threatening language” by the Trump administration against an allied nation was unacceptable.

It’s the latest in a series of crises between the longtime allies. The U.S. has slammed Turkey’s plans to buy a missile defense system from Russia, an issue that’s already raised the threat of American sanctions. The countries have also clashed over the war in Syria, where Turkey has increasingly acted in concert with Russia and Iran. Erdogan blames the U.S. for backing Kurdish militants in Syria, and harboring the alleged mastermind behind the coup attempt against his government.

The Turkish lira extended losses, leading declines among global currencies. It slumped 1.9 percent to 4.864 per dollar, close to a record low, at 9:45 p.m. in Istanbul.

Deal Breakdown

Neither Trump nor the White House offered any immediate details about the measures that the U.S. may take, or how soon they may be imposed. Earlier Thursday, Vice President Mike Pence also blasted Turkey over the pastor’s detention. U.S. officials have also objected to the imprisonment of three consular employees and a NASA scientist as part of Turkey’s post-coup crackdown.

Erdogan’s government arrested Brunson in 2016 and indicted him last year on charges of espionage and attempting to overthrow the state. On Wednesday, after a year-and-a-half in jail, he was released to house arrest.

But that move didn’t assuage U.S. anger.

The escalation of the dispute by Trump and Pence on Thursday reflects frustration over the breakdown of a diplomatic deal that was supposed to have seen Brunson freed and deported back home, according to a person familiar with negotiations. The agreement broke down when Turkey increased its demands for a quid pro quo, calling for the abandonment of U.S. legal action against a Turkish bank blamed for helping evade Iran sanctions, the person said.

State-owned Turkiye Halk Bankasi AS is under criminal investigation in New York’s southern district on the Iran charges. A senior executive at the lender was jailed by a U.S. court in May.

Magnitsky-Style?

Halkbank is seen as a likely target of penalties as a result of the investigation.

Some analysts have also raised the prospect that Trump or the U.S. Congress will impose broader measures, which could target business leaders close to Erdogan’s government along the lines of American sanctions against Russia.

The Senate Foreign Relations Committee on Thursday approved a bill that would commit the U.S. to opposing any credit offers to Turkey by international lenders such as the World Bank’s International Finance Corp. Similar legislation also was introduced in the U.S. House, though any final action in either case would be weeks away.

Pence, who said he spoke to Brunson on Wednesday, described the pastor’s move to house arrest as “a welcome first step” but “not good enough.” Secretary of State Michael Pompeo also said Wednesday that the move to house arrest was insufficient. “We have seen no credible evidence against Mr. Brunson,” he said.

F-35 Freeze

Trump had said last week on Twitter that Turkey’s failure to release Brunson was a “total disgrace.”

The pastor’s detention has come at a critical time in U.S.-Turkey relations. Erdogan has been infuriated by U.S. support for Kurdish rebels in Syria, who he views as linked to domestic terror groups. And his decision to purchase the Russian S-400 missile system has raised questions about Turkey’s role in the North Atlantic Treaty Organization.

The S-400 deal and other tensions have prompted U.S. Lawmakers to call for a halt in sales of F-35 military jets to Turkey, even though several key parts of the fighter are made in Turkey. Defense Secretary Jim Mattis has opposed that effort. Turkey is demanding the U.S. extradite Fethullah Gulen, a cleric and former Erdogan ally living in Pennsylvania, who the Turkish president blames for engineering the 2016 coup attempt.

Trump and Erdogan, who last month won re-election in a vote that granted him broad new powers, were seen speaking at length during a gathering of NATO leaders in Brussels earlier this month.