By Clare Foran, Kaitlan Collins and Nicole Gaouette, CNN    

(CNN) -- President Donald Trump said Friday he has green-lit a doubling of steel and aluminum tariffs on Turkey and warned that relations between the US and Turkey "are not good at this time."

The moves stem from Trump's frustration over a detained American pastor held by Turkey on what US officials say are bogus charges, two sources with knowledge of the President's mindset tell CNN.

"I have just authorized a doubling of Tariffs on Steel and Aluminum with respect to Turkey as their currency, the Turkish Lira, slides rapidly downward against our very strong Dollar! Aluminum will now be 20% and Steel 50%. Our relations with Turkey are not good at this time!," the President tweeted.

In a statement, deputy White House press secretary Lindsay Walters said, "Section 232 tariffs are imposed on imports from particular countries whose exports threaten to impair national security as defined in Section 232, independent of negotiations on trade or any other matter."

Walters did not offer any explanation as to how US national security is threatened by steel and aluminum imports from Turkey, which hosts a major US military base.

The President's announcement Friday could further escalate tensions with Turkey, which continues to detain Andrew Brunson, an American pastor Ankara accuses of helping plot a 2016 coup attempt against Turkish President Recep Tayyip Erdogan. US officials maintain there is no credible evidence against Brunson, and Trump and his administration have negotiated for weeks to secure his release.

Earlier this month, the US slapped sanctions against Turkey's ministers of justice and interior in response to Brunson's detention. Since then, talks over Brunson's release have broken down. On Saturday, Turkey ordered that the assets of the US "justice and interior" secretaries would be frozen.

National Security Council and State Department officials continued to go back and forth with their Turkish counterparts this week, but nothing has been resolved, an official tells CNN. Before the President's trip to Europe last month, officials believed they were close to securing Brunson's release.

"This innocent man of faith should be released immediately!" Trump wrote on Twitter in late July.

That was the same month Brunson was moved from jail to house arrest after being held for more than a year and a half.

Trump and Vice President Mike Pence have had multiple conversations with officials in the Turkish government regarding Brunson, according to an administration official, and Trump and Erodgan discussed Brunson specifically during a call in mid-June. The White House never issued a readout of the call, but confirmed that it happened after the Turkish government disclosed details. It's unclear if the two leaders have spoken since.

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