The United States on Thursday voiced alarm over Ukraine's dismissal of the reform-minded head of the state-owned oil and gas company, urging its ally to do more to improve corporate governance.
The Ukrainian government on Wednesday sacked Naftogaz chief Andriy Kobolev, whose moves toward transparency won him support among Western investors, and suspended all members of the company's supervisory board.
State Department spokesman Ned Price said the United States was "deeply concerned" over the "calculated move," saying it showed "disregard for fair and transparent corporate governance practices."
"Unfortunately, these actions are just the latest example of ignoring best practices and putting Ukraine's hard-fought economic progress at risk," Price told reporters.
"We will continue to support Ukraine in strengthening its institutions, including advancing democratic institutions and corporate governance reforms, but Ukraine's leaders must do their part," he said.
The United States and Western European nations are vital supporters of Ukraine, one of Europe's poorest countries that has been under longstanding pressure to address corruption.
The United States voiced solidarity with Ukraine earlier this month when Russia amassed troops on its border, raising fears.
Kobolev helped wean Ukraine off its dependence on Russian gas after Moscow in 2014 seized Crimea and war broke out in eastern Ukraine with Russian-backed separatists.
The cabinet said it dismissed Kobolev after the company posted losses, but he denounced the decision as politically motivated.