President Trump's announcement Friday morning that he has authorized the doubling of tariffs on steel and aluminum imports coming from Turkey came in a tweet that noted, "Our relations with Turkey are not good at this time!"

He did not offer an explanation for the tariff hike, which raises the tariffs to 20 percent on aluminum and 50 percent on steel, though there are a couple of possibilities. In addition to the steep drop in the Turkish Lira, which effectively reduces the impact of the tariffs, the U.S. has so far been unsuccessful in persuading Turkish President Recep Tayyip Erdoğan to release U.S. pastor Andrew Brunson. Arrested in 2016, he faces terror and espionage charges.

High-level meetings in Washington between U.S. and Turkish officials over Brunson ended this week, apparently without a resolution. The U.S. has already imposed financial sanctions on two Turkish ministers and has warned there could be more measures — the doubling of tariffs might be that move.

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"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!" Mr. Trump tweeted Friday morning. "Aluminum will now be 20% and Steel 50%. Our relations with Turkey are not good at this time!"

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! — Donald J. Trump (@realDonaldTrump) August 10, 2018

White House spokeswoman Lindsay Walters later clarified, "As he stated, the president has authorized the preparation of documents to raise tariffs on imports of steel and aluminum from Turkey. 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."

The Trump administration has called upon Erdoğan to release Brunson for months. In July, the president warned in a tweet that the U.S. "will impose large sanctions on Turkey for their long time detainment of Pastor Andrew Brunson."

"The United States will impose large sanctions on Turkey for their long time detainment of Pastor Andrew Brunson, a great Christian, family man and wonderful human being. He is suffering greatly. This innocent man of faith should be released immediately!" the president tweeted last month.