The Turkish lira weakened to 5.86 against the dollar on Friday from its previous close of 5.8150 as investors weighed up a United States warning that Turkey should expect more economic sanctions unless it hands over detained American pastor Andrew Brunson.
Ankara accuses Mr Brunson - who operates a tiny evangelical church in Izmir - of having links to the outlawed Kurdistan Workers Party and the Gulenist movement, which Turkey blames for a failed coup two years ago.
In recent weeks, the U.S. has sanctioned a pair of Turkish cabinet members, and dramatically increased tariffs against the nation, fueling anger among Turkish leaders and creating economic uncertainty across the region.
"We have stood together and will continue to do so", he said, making clear the high-level meeting was meant to communicate unequivocal support for Turkey at a critical juncture.
"They want to hold our wonderful pastor", Trump added.
The investment package was announced after Qatar's Emir Tamim bin Hamad Al-Thani met President Tayyip Erdogan in the capital, as Turkey grapples with a collapsing lira and a worsening commercial and political standoff with North Atlantic Treaty Organisation ally the United States.
Turkey says the case is a matter for the courts.
The United States imposed sanctions on two Turkish government ministers, and last week Washington raised tariffs on Turkish metal exports causing the lira currency to drop.
In this file photograph taken on 25 July 2018, U.S. pastor Andrew Craig Brunson is escorted by Turkish plain clothes police officers to his house in Izmir.
He later tweeted: "Turkey has taken advantage of the United States for many years".
The issue has led to a dramatic souring of U.S. -Turkey relations. On Monday the lira hit a record low of 7.2, dragging down other emerging markets currencies. Turkey, for its part, denounced the "economic war" and said it would find "new friends and allies".
"There has been no improvement in relations with the USA and additional sanctions may be on the horizon", said William Jackson of Capital Economics in a note to clients, adding that the lira could see a downward trend in 2019 and beyond.
Ratings agency Standard & Poor's is scheduled to release a review of Turkey's sovereign credit rating after the market close on August 17.
A money changer counts Turkish lira banknotes at a currency exchange office in Istanbul, Turkey Aug. 2, 2018.
Investors are concerned that Turkey has amassed high levels of foreign debt to fuel growth in recent years.
Following the Qatar news, the lira firmed briefly to 5.8699 from 6.04 to the dollar, before easing back to 6.0500 by 1658 GMT.