White House National Security Advisor John Bolton met Turkish ambassador to Washington Serdar Kılıç amid tensions over Turkey's detainment of terror-linked pastor Andrew Brunson, sources said late Monday.

The relations between the two NATO allies deteriorated to an unprecedented extent earlier after the U.S. imposed sanctions on Interior Minister Süleyman Soylu and Justice Minister Abdulhamit Gül for not releasing Brunson, who faces terrorism charges in Turkey.

The sanctions were issued under "Executive Order (E.O.) 13818, 'Blocking the Property of Persons Involved in Serious Human Rights Abuse or Corruption,' which builds upon Treasury's Global Magnitsky Act authorities," the statement added.

The Global Magnitsky Act of 2016 enables the U.S. government to target entities that it claims participate in human rights violations or corruption anywhere in the world. The act allows for travel bans, seizure of U.S. assets and prohibitions on conducting business with U.S. entities.

Brunson, who was previously jailed for his links to the Gülenist Terror Group (FETÖ) and the PKK, was released from prison on July 25 following an appeal by his lawyer, who objected to his extended detention in an earlier hearing, citing health problems that the 50-year-old defendant suffers from.