(This story was edited after posting to correct a transcription error in the quote of Stavridis in the eighth paragraph.

Adm. James Stavridis, who left his post as the first Navy man to command NATO last year and is now the dean of Tufts University's Fletcher School of Law and Diplomacy, thinks the Obama administration has gotten things about right in its response to Russia's military incursion into Ukraine's Crimea region.

Which is not to say he's sanguine about developments. Far from it. But in a brief interview yesterday, he stressed reducing international military tension over Ukraine while trying to find ways to isolate Russia over its current course.

Earlier this month, Stavridis wrote a short piece for Foreign Policy with a list of suggestions for the US and NATO. He stressed the need for increased electronic and satellite surveillance of the area, information-sharing with the Ukrainian military, contingency planning for a possible full-scale Russian invasion of Ukraine, and moving NATO forces into the Black Sea, among other things.

Stavridis reckons most of that has been done since he wrote his piece. But the situation has grown more dangerous since, with the addition of Russian troops to Crimea and a buildup of Russian forces on the border with eastern Ukraine.

What are the next steps? We only spoke briefly, but he spoke of sanctions.

"Sanctions targeting individuals?" I asked. He responded that he'd start there, but said the US and its European partners should consider broader sanctions targeting the Russian economy, particularly focusing on the oil and gas industry that contributes about 25 percent of Russia's GDP (by comparison, the US, no energy slouch, obtains about 2.5 percent of its GDP from the oil and gas business).

He said the Russian economy, as a "one-trick pony," was vulnerable. He also said that he's worried about the precedent of Russia's moves to separate Crimea from Ukraine.

"This does not only violate international law ... but it's also breaking an important international norm," he said.

The US and Europe are also moving in the direction of serious sanctions. Germany's Bild newspaper reports today, citing "European officials," that the CEOs of Russian energy giants Rosneft and Gazprom are on a list of names of about 120 Russians who could be hit with asset freezes and travel bans as soon as next week.

The Russian-sponsored referendum on Crimea, guarded and overseen by Russian troops, is scheduled to go forward on Sunday – with no option given to voters to remain part of Ukraine. The choices are union with Russia or de facto independence. Ahead of the vote there are reports that anti-referendum activists have been detained in Crimea by pro-Russian officials.

US Secretary of State John Kerry met with Russian Foreign Minister Sergei Lavrov for more than five hours in London today, and undoubtedly told him that the chance of serious sanctions will go up substantially if the referendum goes forward. The Russians didn't budge.

Are sanctions that target Russian energy exports possible? For them to work, the European Union would have to be fully on board – and many EU states are heavily reliant on Russian-supplied energy.

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However, German Chancellor Angela Merkel, who has been a key interlocutor between Russia and the West – and whose country has significant economic interests at stake – has indicated a willingness to get tough. If negotiations over Crimea are not effective, she warned Thursday, the West would take measures that "will cause damage to Russia, both economically and politically" – a reference to sanctions.

If Russia makes more belligerent moves toward Ukraine, the chances of an economic showdown increase.