The increased economic pressure is designed to end the insurgency in eastern Ukraine that is widely believed to be backed by Russia.
Obama says he prefers a diplomatic solution but that Russia hasn't shown that it is committed to ending the conflict.
The latest U.S. sanctions target leading Russian energy firms and financial institutions, as well as Russian companies that make weapons. Officials say the ability of these entities to access U.S. capital markets will be limited.
An adviser to Russian President Vladimir Putin and three other individuals were also targeted.
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