Ukrainian Defense Minister Valeriy Heletey said Monday that the army would stop trying to remove separatists from the east, moving instead to a defensive strategy against what he called a “full-scale invasion” of Russian regular troops…

The White House hopes that Mr. Obama’s stop in Tallinn will send a clear message to Russian President Vladimir Putin : Don’t touch the Baltics.

“Russia, don’t even think about messing around in Estonia or in any of the Baltic areas in the same way that you have been messing around in Ukraine,” said Charles Kupchan, the White House’s senior director for European affairs.

So far, though, Mr. Putin has appeared undaunted by warnings from the West or a growing catalog of sanctions.