As he opens up a visit to Europe likely to be dominated by the crisis in Ukraine, President Barack Obama is warning that if Russia continues to escalate its intervention into Ukraine, the U.S. and Europe “need to be prepared to impose a greater cost.”

In an interview with the Dutch newspaper, de Volkskrant, ahead of arriving today in The Netherlands, Obama defended his foreign policy approach that emphasizes diplomacy, but said the U.S. and Europe can not allow Russia to annex Crimea without consequence.

“In all my discussions with European leaders, my message will be that Russia needs to understand the economic and political consequences of its actions in Ukraine,” said Obama, who meets today with leaders of the seven largest industrialized countries to discuss the situation in Ukraine. “We simply cannot have countries violating the sovereignty and territorial integrity of other nations. We cannot have countries purporting to annex parts of independent nations. The international law and principles at the heart of our international system have to mean something.”

The U.S. last week ratcheted up a series of economic sanctions against allies of Russian President Vladimir Putin and Obama is under pressure on the trip to convince European allies to step up. Many are leery, given Europe’s trade and energy reliance on Russia — a fact highlighted by the newspaper, which said Obama would be meeting with Dutch prime-minister, Mark Rutte, whom the reporter noted is “reluctant to impose harsh actions” on Russia.