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European Union leaders agreed Thursday to slap sanctions on a dozen more Russian officials tied to Moscow's annexation of Crimea from Ukraine, bringing the number of people facing an EU blacklist to 33.

The bloc said it had resolved the expand the list of people subjected to sanctions by 12 names — and cautioned that it would subject Russia to additional economic measures if the crisis in Ukraine escalates.

The agreement followed President Barack Obama's announcement Thursday that he had ordered sanctions against nearly two dozen members of President Vladimir Putin's inner circle and signed an executive order giving the U.S. authority to impose sanctions on "key sectors of the Russian economy."

The 28-nation group did not immediately disclose the names of those facing travel bans and asset freezes — but they are widely expected to target those close to Putin as punishment for his takeover of the Crimean peninsula.

Earlier on Thursday, EU leaders also announced plans to cancel a scheduled EU-Russia summit in June amid escalating tensions over Ukraine.

The Associated Press and Reuters contributed to this report.