U.S. President Donald Trump said he was “very angry” at Vladimir Putin and threatened “secondary tariffs” on buyers of his country’s oil if the Russian leader refuses a ceasefire with Ukraine.

In comments reported by NBC News, Trump said he was “pissed off” at Putin for casting doubt on Ukrainian President Volodymyr Zelenskyy’s legitimacy as a negotiating partner, and threatened curbs on “all oil coming out of Russia.” He later added that he didn’t think the Russian president would “go back on his word.”