The US has threatened to impose more economic sanctions on Turkey if it does not free a detained American pastor.
Andrew Brunson has been held in Turkey for nearly two years over alleged links to outlawed political groups.
The dispute over his release has seen the two Nato allies impose tariffs on one another's goods.
This has worsened a crisis for Turkey's currency, the lira, which has lost about a third of its value against the dollar since January.
The crisis has prompted widespread selling in other emerging markets, sparking fears of a global crisis.
What is the new threat from the US?
The lira has staged a small recovery but that is threatened by a fresh tweet from US President Donald Trump.
He said early on Friday that Turkey had "taken advantage of the United States for many years" and that he was "cutting back on Turkey".
