President Donald Trump's decision to double U.S. tariffs on steel and aluminum imports from Turkey is "brutal," the director of the European Council on Foreign Relations said.

Carl Bildt, the former prime minister of Sweden who is now the co-chair of the European Council on Foreign Relations, tweeted on Friday: "To double key tariffs against an ally which is in a difficult financial crisis is really brutal. Really."

U.S. President Donald Trump announced Friday on Twitter that he had authorized the doubling of steel and aluminum tariffs with respect to Turkey, as tensions mounted between the two NATO allies.

"Our relations with Turkey are not good at this time!" Trump said.

The tweet was another salvo in the growing dispute between Turkey and the U.S.

Earlier this week, a Turkish delegation returned from Washington with no progress on the detention of American pastor Andrew Brunson, who is under house arrest in Turkey on terrorism charges.

Brunson's charges include spying for the PKK, listed as a terrorist group by both the U.S. and Turkey, and the Gülenist Terror Group (FETÖ), the group behind the defeated coup attempt in Turkey of July 2016.

The United States, the world's biggest steel importer, imposed tariffs of 25 percent on steel and 10 percent on aluminum in March for imports from a variety of countries, in a move that provoked counteraction from trade allies.

Turkey retaliated against the move by slapping import duties on $1.78 billion worth of U.S. products, including coal, paper, nuts, whiskey, autos, machinery and petrochemicals.