U.S. President Donald Trump has threatened to slap sanctions on fellow NATO member Turkey unless the government of Recep Tayyip Erdogan releases an American pastor detained for almost two years. Andrew Brunson, who last week was transferred to house arrest after being jailed for 21 months, is accused by Ankara of supporting exiled Turkish cleric Fetullah Gulen—who, in turn, is blamed by Erdogan for orchestrating the 2016 failed coup. President Trump upped his rhetoric against Turkey following a purported failed bid to secure Brunson’s full release, which, according to the Washington Post, included Israel freeing a Turkish woman with alleged ties to Hamas at the direct request of the American leader. In response, Erdogan has vowed to “not take a step back” while warning that ties with the U.S. could be irreparably damaged by the ongoing dispute. This comes as Turkey is increasingly perceived to be straddling the fine line between West and East, with Ankara’s longstanding relations with Washington and European capitals strained by Turkey’s burgeoning diplomatic, economic and military ties to Russia, China and even Iran.