Andrew Brunson, an evangelical pastor from Black Mountain, N.C., shown in Izmir, Turkey, on July 25. (Emre Tazegul/AP)

The United States will take further action against Turkey if it continues to detain American pastor Andrew Brunson, Treasury Secretary Steven Mnuchin said Thursday in a sign that tensions between the NATO allies will continue to escalate over the issue.

“We have more that we’re planning to do if they don’t release him quickly,” Mnuchin said when asked by President Trump at a Cabinet meeting for an update on U.S. sanctions on Turkish officials.

He did not provide further details.

Brunson is under house arrest after spending nearly two years in a Turkish prison under what the Trump administration has said are bogus allegations of aiding terrorists.

The issue has led to a dramatic souring of U.S.-Turkey relations. The Treasury Department earlier this month levied sanctions on two senior Turkish officials in retaliation for Brunson’s continued detention. That move was followed by an announcement by Trump last week that the United States was doubling tariffs on imported Turkish metals.

Turkey has responded by declaring that it will raise tariffs on a number of U.S. imports, including cars, tobacco and spirits.

In remarks at Thursday’s Cabinet meeting, Trump voiced his disappointment with Turkey in personal terms, saying the country has “not proven to be a good friend.”

“They have a great Christian pastor there. He’s a very innocent man,” Trump said.

He also appeared to acknowledge that he was disappointed that Turkey did not release Brunson after the United States helped negotiate the release of a Turkish national being held in Israel.

“We got somebody out for him,” Trump said, referring to Turkish President Recep Tayyip Erdogan. “He needed help getting somebody out of someplace; they came out.”

“They want to hold our wonderful pastor,” Trump added. “Not fair. Not right.”

Karen DeYoung and Kareem Fahim contributed to this report.