United States Secretary of State John Kerry cautioned Monday (July 18) that Turkey’s membership in  Nato could be jeopardised if it  abandons democratic principles and the rule of law in a post-coup crackdown, the Washington Post reports.

“Nato also has a requirement with respect to democracy,” Kerry told reporters after European Union foreign policy chief Federica Mogherini warned Turkey not to execute coup plotters. She noted that countries with the death penalty cannot join the European Union, as Turkey has sought to do.

Kerry said Turkish Foreign Minister Mevlut Cavusoglu has repeatedly assured him that the government will respect democracy and the law.

Kerry warned that Nato will “measure” its actions. “Obviously a lot of people have been arrested and arrested very quickly,” Kerry said. “The level of vigilance and scrutiny is obviously going to be significant in the days ahead. Hopefully we can work in a constructive way that prevents a backsliding.”