President Barack Obama said on Sunday it was necessary to send a message to Russia that its "destabilizing" actions in eastern and southern Ukraine must stop, as the United States and its European partners prepared to impose new sanctions on Moscow.
Speaking at a news conference during a visit to Malaysia, Obama said any decision on whether to slap "sectoral" sanctions on the Russian economy at a later time would depend on whether the United States and its allies could find a unified position on how to proceed.
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The next round of sanctions, which could be unveiled as early as Monday, are expected to target Russian individuals and entities but are not likely to directly hit sectors of the Russian economy such as energy, which would also hurt the Europeans.
"We're going to be in a stronger position to deter Mr Putin when he sees that the world is unified and the United States and Europe is unified rather than this is just a U.S.-Russian conflict," Obama told reporters.
He said Russia had not "lifted a finger" to get pro-Russian separatist rebels in Ukraine to comply with an international agreement to defuse the crisis.
"In fact, there's strong evidence that they've been encouraging the activities in eastern and southern Ukraine," he said.