US President Donald Trump and Vice-President Mike Pence have threatened Turkey with sanctions if it fails to release jailed pastor Andrew Brunson.
The evangelical from North Carolina has been in detention for nearly two years, accused of having links to banned political groups.
However, President Trump demanded his immediate release, or Turkey, a Nato ally, would face “large sanctions”.
The Turkish foreign ministry called the US demands “unacceptable”.
“No-one can give orders to Turkey and threaten our country,” said spokesperson Hami Aksoy.
Who is Andrew Brunson?
He is a long-term resident in Turkey. He lived with his wife and three children while working as the pastor of the small Izmir Resurrection Church, which had a congregation of about two dozen Protestants.
The authorities accuse him of having links with the outlawed Kurdistan Workers’ Party (PKK) and the Gulenist movement, which Turkey blames for a 2016 failed coup.
Mr Brunson has denied charges of espionage, but faces up to 35 years in jail if found guilty.
He was moved into house arrest on Wednesday for health reasons, but US Secretary of State Mike Pompeo said this was not enough.
- US pastor leaves prison in Turkey
- Who are the Gulenists?
“We have seen no credible evidence against Mr Brunson,” Mr Pompeo tweeted on Wednesday.
Turkey’s foreign ministry said it had shared “necessary information” with the US, but insisted the case should be left with its independent judiciary.
Why is the US speaking out?
Mr Pence also sent out a series of strongly worded tweets, saying Turkey must act immediately or “be prepared to face the consequences”.
The vice-president, who is himself an evangelical Christian, attended the global summit on religious freedom at the state department on Thursday, which is thought to have sparked the outburst.
Mr Pompeo, who is also an evangelical, hosted the summit – the first of its kind to be held at the state department.