Trade between the US and Russia grew strongly in March, even though Washington slapped sanctions on Moscow after its annexation of Crimea. US exports to Russia increased 9 percent from February compared to the same period last year, while imports from Russia grew 36 percent from February compared to last year, according to the US Commerce Department.

Meanwhile, EU imports from Russia contracted more than 9 percent during the first quarter of this year compared to the same period last year, while EU exports to Moscow fell more than 10 percent compared to the first three months of 2013, according to Eurostat.

While these figures indicate that trade between the EU and Russia reacts more strongly to external influences than that between Russia and the US, they don't tell the whole story. Add to this that the EU is Russia's number one trading partner, but that Russia isn't even among Washington's top 15 trading partners and it becomes clear why Europe is much more hesitant about imposing tough economic sanctions than the US.

Nothing to lose

"The US has nothing to lose and the EU does, so it's not an equal situation," said David Marples, a Russia and Ukraine scholar at the University of Alberta about the different stances on sanctions.

US officials have been unhappy with what many consider Europe's half-hearted response to Russia's behavior vis-à-vis Ukraine for a long time.

That's why President Obama took to the phone himself for a conference call with European leaders at the end of April to get them to agree on tougher economic sanctions against Moscow.

From a US perspective, the result was mixed at best. Many of its European partners still had strong reservations about tougher sanctions which makes a unified European stance hard to achieve.

In the end, Washington's call for tougher sanctions resulted in Obama and German Chancellor Angela Merkel defining a new trigger for economic measures at a joint appearance in the White House Rose Garden. Instead of a Russian intervention in Ukraine, so called third phase sanctions would now be implemented should Moscow interfere with Ukraine's election.

What that means concretely is whether the 28 EU countries will in fact sign up for tougher sanctions if push comes to shove. It is still anyone's guess. While some of that may be due to what has been called constructive ambiguity, the ongoing debate over sanctions again highlights a gap between the EU and the US.

Diverse group

"The United States would like to see the EU take a stronger line," says Marples, but the EU is not a single political entity. "It consists of a lot of countries that have diverse attitudes towards what's happening in Ukraine and Russia. So it's unreasonable to suggest that the EU should take an absolutely firm stance."

Andrew Michta, a senior fellow with the Center for European Policy Analysis in Washington contends that the EU has economically much more to lose than the US and that it's difficult for the EU to speak with one voice on this issue, but that this shouldn't override Europe's strategic interests.

"I would not give the EU a pass because it is too cumbersome and difficult to act. I would say the key issue is what the big three Germany, France and the UK see their commercial interest and their ties to be."

Business trumps strategic interests

The EU, says Michta, has tried to integrate Russia economically for which it is now paying the price: "The result we have today, and I think this is Putin's calculation, is that he has in effect a ready-made lobby in Europe. Not in any shape or form particularly rooting for Russia, but having lots to lose in terms of business connectivity with Russia."

He points to France's controversial sale of two assault ships to Moscow and Chancellor Merkel's remark in a recent interview in which she condemned Russia's behavior, but said that in the long term a close partnership with Russia was necessary as examples of how in Europe business connectivity with Russia trumps strategic thinking.

Sure the EU could hit Russia where it hurts economically, says Marples. As the biggest foreign investor, "if they pulled out, it could cause catastrophe for Russia, but of course it works both ways. I think the EU doesn't really want to put a noose around Russia's neck. It's not really in the EU's interest to do so."

What's more, notes Marples, the US stance towards Russia is also more careful than forceful. "From the United States you see a lot of rhetoric, but you don't see a lot of hard action outside of what NATO is doing in the border countries which is kind of a belated reaction. But I don't think it's going much further on the US part either."