President Tayyip Erdogan said on Tuesday that Turkey would boycott electronic products from the U.S., which has imposed sanctions and raised tariffs against Ankara in a dispute about the detention of a U.S. evangelical pastor.

Erdogan said Turkey has been taking necessary measures regarding the economy, amid a slide in the lira currency exacerbated by the dispute with Washington, but it was important to keep a firm political stance.

“Switching to foreign currency would mean giving in to the enemy, Erdogan said.

Tensions between the two NATO allies have intensified amid a dispute over the detention of the Brunson, whose cause has been championed by Vice President Mike Pence.

Erdogan, has signaled defiance, saying the U.S. “cannot tame” his country with threats and warning that Trump was risking the loss of a strategic ally.

President Donald Trump’s top national security aide warned Turkey’s ambassador on Monday that the U.S. has nothing further to negotiate until a detained American pastor is freed.

According to two people familiar with the matter, signaling a standoff between the countries will continue as Turkey’s financial meltdown spread to emerging markets.

White House National Security Adviser John Bolton delivered that message to Amb. Serdar Kilic in Washington asking for room to discuss the encounter.

The White House said that Kilic had requested the meeting, which centered on the Ankara government’s detention of an American evangelical pastor, Andrew Brunson.

Turkey’s failure to free Brunson has become the latest conflict between the two nations.