Ukraine’s president said on Tuesday world powers should keep sanctions on Russia, rejecting U.S. President Donald Trump’s proposal to consider reducing the penalties if Moscow proved a useful ally.

Petro Poroshenko told reporters that sanctions remained the only way to keep Russia at the negotiating table over the crisis in eastern Ukraine, that Western powers say has been fueled by Moscow.

The United States, the European Union and others imposed sanctions on Russia in 2014 over its annexation of the Crimea peninsula from Ukraine and its support for pro-Russia separatists in Ukraine’s east.

But Trump told the Wall Street Journal this month he might do away with some penalties if Moscow proved helpful in battling Islamist militants and reaching other goals important to Washington.

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