As the deadlock over a detained U.S. pastor remained unsolved, the White House said Monday that U.S. National Security Advisor John Bolton met with Turkish Ambassador to the United States Serdar Kilic.

　　U.S. National security adviser John Bolton speaks during the daily press briefing at the White House, Thursday, Aug. 2, 2018, in Washington. [File photo: AP/Evan Vucci]

　　According to a statement issued by White House Press Secretary Sarah Sanders, Bolton met with Kilic in the White House "at the Turkish Ambassador's request."

　　"They discussed Turkey's continued detention of Pastor Andrew Brunson and the state of the U.S.-Turkey relationship," the statement read, without giving further details.

　　The statement came as the two nations continued to wrangle over U.S. pastor Andrew Brunson, who was charged with involvement in a failed coup attempt against President Recep Tayyip Erdogan's government in 2016.

　　Transferred from detainment to house arrest last month, he could face up to 25 years in jail if found guilty.

　　U.S. President Donald Trump tweeted Friday that he had authorized to double the tariffs on steel and aluminum products from Turkey to 50 percent and 20 percent respectively. The White House confirmed the tweet.

　　The United States also slapped sanctions on two Turkish ministers over the case earlier in August.

　　In response, the Turkish Foreign Ministry vowed to "retaliate" against U.S. "aggression" over the case of Brunson "without any delay," and called on Washington to reverse its decision.