Secretary of State John Kerry recently urged Russian leader Vladimir Putin to dial down the confrontation in Ukraine. "If Russia continues in this direction," Kerry warned, "it will not just be a grave mistake, it will be an expensive mistake."

So far, however, it's the leaders in Washington, Bonn and Brussels who are making mistakes -- not Moscow. President Obama and his allies are not following through on their threats. And their timidity could be both expensive and dangerous.

It's clear by now that Putin is a bully, a bully who pushes others around until someone calls his bluff. But instead of standing up, the West is backing down.

The economic sanctions announced by Washington this week are a tap on the shoulder, not even a slap on the wrist: freezing the assets of 17 companies; denying travel visas to seven business leaders; blocking the export of militarily useful technology.

Russian investors were so relieved that the Moscow stock market actually went up. Even the Obama administration conceded the weakness of its actions. "We don't expect there to be an immediate change in Russian policy," a senior official told reporters.

Really? If you expect no change, then why bother? All you do is embolden Putin and his surrogate bullies, swaggering around Ukraine in their black ski masks, seizing international monitors, occupying government buildings, raising Russian flags.

The Washington Post editorial board got it right: "By choosing not to use the economic weapons at its disposal and broadcasting that restraint to the world, Mr. Obama is telling Mr. Putin as well as other potential aggressors that they continue to have little to fear from the United States."

When Putin has "little to fear," the fear factor for everybody else shoots up. Sure, Washington is 4,857 miles from Moscow, a long way for a bully to reach. But Riga, the capital of Latvia? It's 570 miles from the Kremlin. How do you think the Latvians -- and the Estonians and the Lithuanians and the Moldovans -- are feeling right now? Safe? Reassured?

During his recent trip to Asia, the president offered an insight into his foreign policy thinking. "Typically, criticism of our foreign policy has been directed at the failure to use military force," he told a questioner in Manila. "And the question I think I would have is, why is it that everybody is so eager to use military force after we've just gone through a decade of war at enormous costs to our troops and to our budget?"

Obama is setting up a straw man. Military force should always be a last option, but even his harshest critics are not suggesting that he physically dislodge the Russians from Ukraine. His error is not using the "economic weapons" described by the Post.

In this case, traders are more powerful than tanks; investors, more influential than infantry. Putin's real weakness is the marketplace, not the battlefield.

The ruble has lost 7.6 percent of its value against the dollar since the beginning of the year; the Moscow stock market is down 13 percent. Standard and Poor's, the financial rating agency, dropped its grade for Russian bonds to one notch above junk status and warned investors that further economic sanctions could "undermine already weakening growth prospects."

In the first three months of the year, $51 billion in capital fled Russia. In a desperate move to block the exits, central bankers in Moscow raised interest rates -- twice -- to 7.5 percent.

To be sure, Obama is restrained by his European allies, whose greater economic stake in Russia makes them more reluctant to confront Putin. American trade with Russia amounts to $26 billion annually, compared to Europe's $370 billion.

Joe Kaeser, the head of giant German company Siemens, actually went to Moscow, met with Putin, took photos with him and gave him a "vote of confidence," as the Wall Street Journal put it. Poor show, Joe.

But that's exactly why Putin is so vulnerable. He needs the West -- to buy Russian goods, especially gas and oil; to build Russian infrastructure; to invest in Russian bonds. If he didn't crave a "vote of confidence" from the head of Siemens, he'd be far more lethal.

Obama calls the latest round of sanctions the "next stage in a calibrated effort to change Russia's behavior." And rashness can be just as damaging as timidity. But the evidence seems clear: Obama's calibrations are off-key. Russia's behavior is not changing. It's time to turn up the heat and make the bully sweat.

Steve and Cokie Roberts can be contacted by email at stevecokie@gmail.com.