US President Donald Trump on Friday said the United States was not going to take Turkey's detention of US Christian pastor Andrew Brunson "sitting down", a day after his Treasury chief said Washington could hit Ankara with further sanctions.

"They should have given him back a long time ago, and Turkey has in my opinion acted very, very badly," Trump told reporters at the White House. "So, we haven't seen the last of that. We are not going to take it sitting down. They can't take our people."

A Turkish court rejected an appeal to release Brunson from house arrest, broadcaster Haberturk said on Friday.

Brunson, an Evangelical pastor from North Carolina residing in the coastal province of Izmir, is standing trial in Turkey over terrorism charges. He has lived in Turkey for two decades.

His case now lies at the heart of a diplomatic crisis between Turkey and the United States that has prompted a crash of Turkey's lira currency.

The lira, which has lost some 40 per cent of its value this year, weakened beyond 6.21 against the US dollar after the news, from 6.04 beforehand.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.