President Recep Tayyip Erdogan has warned the U.S. nothing will force Ankara to “step back” after President Donald Trump threatened “significant sanctions” against Turkey if a jailed U.S. pastor is not released.

“You cannot make Turkey take a step back with sanctions,” Mr. Erdogan said in his first comments since relations soured after Mr. Trump raised the issue of detained Pastor Andrew Brunson on Thursday.

“The US should not forget that it could lose a strong and sincere partner like Turkey if it does not change its attitude,” Mr. Erdogan was quoted as saying by Hurriyet daily.

Relations between the NATO allies have worsened over the jailing of Brunson, who ran a Protestant church in the Aegean city of Izmir.

Last Thursday U.S. Vice President Mike Pence told participants at the State Department’s first Ministerial on Religious Freedom that the U.S. patience is running out on the matter and Turkey faced a clear choice of releasing its detainee or being hit by sanctions. He said:

To President Erdogan and the Turkish government, I have a message on behalf of the United States of America: Release Pastor Andrew Brunson now or be prepared to face the consequences. If Turkey does not take immediate action to free this innocent man of faith and send him home to America, the United States will impose significant sanctions on Turkey until Pastor Andrew Brunson is free.

President Trump echoed that call soon after:

The 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! — Donald J. Trump (@realDonaldTrump) July 26, 2018

Ties had already been strained over multiple issues including Washington’s support of a Syrian Kurdish militia which Turkey views as a terrorist group and the failure to extradite the Pennsylvania-based Muslim preacher Fethullah Gulen.

Ankara accuses Gulen of links to U.S. security agencies while ordering the 2016 failed overthrow of Erdogan, a claim he strongly denies.

The Washington Post on Friday reported a deal between Ankara and Washington was made to secure the release of a Turkish woman imprisoned in Israel in exchange for the freedom of Brunson.

Ebru Ozkan, 27, had been held for over a month by Israel on charges of passing hundreds of dollars to a “terrorist” group but returned to Turkey on July 16.

The newspaper said the agreement was “personally sealed” by Trump but fell apart when Brunson was transferred to house arrest.