US president Donald Trump has warned Turkey that he will “pay nothing” to secure the release of imprisoned American pastor and “great patriot”, Andrew Brunson.

“We will pay nothing for the release of an innocent man, but we are cutting back on Turkey!” a tweet from the president late on Thursday said.

On Friday, Turkey threatened further action if the US followed through on several promises to levy heavy sanctions unless Mr Brunson was released.

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Mr Brunson’s fate has become the epicentre of a diplomatic spat between the two Nato allies which has sent the Turkish lira tumbling and sparked fears the already fragile economy could collapse.

The lira plummeted to just 5.8 against the dollar and 6.7 against the euro on Friday, compared to just over seven to the dollar a few days earlier. It has lost 40 per cent of its value since the beginning of the year.

The Turkish ambassador to the US met with Mr Trump’s national security advisor John Bolton earlier this week, Reuters reported, and offered to tie conditions to Mr Brunson’s release.

Election in Turkey: the reaction in pictures Show all 10 1 /10 Election in Turkey: the reaction in pictures Election in Turkey: the reaction in pictures Supporters of Mr Erdogan celebrate in Istanbul Getty Election in Turkey: the reaction in pictures A supporter of Mr Erdogan carries his portrait in front of a Turkish flag Reuters Election in Turkey: the reaction in pictures Following the election, a shipowner reads a newspaper that covers the result AP Election in Turkey: the reaction in pictures Supporters of Muharrem Ince, defeated opposition candidate, wait outside the Republican People's Party (CHP) headquarters following Mr Erdogan's claim of victory Getty Election in Turkey: the reaction in pictures People in an Instanbul barber shop listen to Muharrem Ince's speech following the results EPA Election in Turkey: the reaction in pictures Supporters of the pro-Kurdish People's Democratic Party (HDP) hold photos of its leader Selahatin Demirtas AFP/Getty Election in Turkey: the reaction in pictures Supporters of Mr Erdogan celebrate outside the AK party HQ in Ankara Getty Election in Turkey: the reaction in pictures Mr Erdogan waves to supporters in Ankara AP Election in Turkey: the reaction in pictures Mr Erdogan waves to supporters in Ankara AP Election in Turkey: the reaction in pictures Supporters of Mr Erdogan light flares as they celebrate the result AP

Mr Bolton reportedly dismissed the offer.

“[Turkey] missed a big opportunity. This is very easy to resolve,” an unnamed US administration official said. “They made a big mistake trying to tie this to other things.”

Mr Trump’s new warning comes on top of remarks from Steven Mnuchin, the US treasury secretary, who suggested at a cabinet meeting on Thursday another round of tit-for-tat sanctions was imminent.

“They have not proven to be a good friend,” Mr Trump said of Turkey during the meeting. “They have a great Christian pastor there. He’s an innocent man.”

Mr Brunson, an evangelical pastor and American citizen who has lived in Turkey for decades, was detained in Izmir in October 2016 on terror-related charges after the failed July military coup.

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More than 50,000 people remain in prison facing allegations of involvement in the coup, which led to a two-year state of emergency and a crackdown on opposition to president Recep Tayyip Erdogan.

Ties between Ankara and Washington have also soured over Turkey’s state-owned Halkbank, which the US says should be fined for allegedly helping Iran evade US sanctions, and Turkey’s unfulfilled demand that the US extradite Turkish cleric Fethullah Gulen, whom Turkish authorities hold responsible for the 2016 coup.

Last week, Mr Trump tweeted that his administration was sanctioning two Turkish officials and doubling aluminium and steel tariffs for Turkey.