President Donald Trump thanked Turkey on Saturday for freeing American pastor Andrew Brunson after two years in custody and said it would help improve strained relations, but Trump denied cutting a deal for Brunson's release.

"I don't make deals for hostages. There was, however, great appreciation on behalf of the United States, which will lead to good, perhaps great, relations between the United States & Turkey!" Trump wrote in a tweet on Saturday morning.

Brunson, who had been under house arrest since July, was flown out of Turkey on Friday, and Trump said he would meet him at the White House on Saturday.

Relations between the two NATO allies have been strained by US support for Kurdish fighters in northern Syria, Turkey's plans to buy a Russian missile defense system, and the US jailing of an executive at a Turkish state bank in an Iran sanctions-busting case.

The dispute over Brunson brought new tension to the relationship. Trump authorized a doubling of duties on aluminum and steel imported from Turkey in August, and Turkey retaliated by increasing tariffs on US cars, alcohol and tobacco imports.

Turkey is in a financial crisis and its lira currency has plunged against the dollar this year on concerns over President Tayyip Erdogan’s grip on monetary policy and the diplomatic dispute between Ankara and Washington.

Trump specifically thanked Erdogan in his tweet on Saturday.

Brunson was accused of links to Kurdish militants and supporters of Fethullah Gulen, the cleric blamed by Turkey's government for a coup attempt in 2016. Brunson, who lived in Turkey for more than 20 years, denied the accusations and Washington had demanded his immediate release.