The move appears designed to make it harder for U.S. President-elect Donald Trump to roll back the sanctions after Obama leaves office on January 20. Trump has said he wants to improve relations with Russia and would take a second look at the sanctions, although several of his chosen cabinet members said this week that they support the sanctions.

Read alsoUkrainian ambassador voices view of U.S. stance on RussiaIn extending the sanctions, which were due to expire in March 2017, Obama said the Russian government and other people and organizations targeted by the sanctions have "undermined democratic processes and institutions in Ukraine" by their "use of force in Ukraine" and thereby "threaten its peace, security, stability, sovereignty, and territorial integrity."

Because of the threat to Ukraine, Obama said, Russia's actions "pose an unusual and extraordinary threat to the national security and foreign policy of the United States."

The European Union has parallel sanctions on Russia that are due to expire in July. Italy and other EU members have said they would push to end the sanctions, especially if Trump carries out a softening of U.S. policy towards Russia.