German Chancellor Angela Merkel and Russia's President Vladimir Putin (C) listen to French President Francois Hollande during a meeting on resolving the Ukraine crisis at the Kremlin in Moscow February 6, 2015. (Maxim Zmeyev/Reuters)

THOUGH PRESIDENT Obama has yet to agree, proposals that the United States supply Ukraine with defensive weapons have already had a tangible impact. On Friday, they prompted German Chancellor Angela Merkel and French President François Hollande to rush to Moscow in what looked like a long-shot attempt to broker a peace deal with Vladi­mir Putin. Ms. Merkel canceled a proposed summit in Kazakhstan with Mr. Putin weeks ago because of the dim prospect that the Russian ruler would agree to respect the cease-fire his government agreed to in September. That she suddenly decided to pay court at the Kremlin seemed to reflect not any softening of the Russian position but rather a spiking of European anxiety.

The results of the Moscow meeting appeared to be inconclusive. But Mr. Putin certainly seemed to receive his visitors from a position of strength. Unlike the Europeans, he is clearly not concerned about “escalation,” having just dispatched hundreds of tanks and other weapons systems, as well as fresh troops, to lead a new offensive in eastern Ukraine. Nor does he appear motivated to settle with the West: An undisclosed Russian proposal delivered to Ukraine this week was described as “cynical” and “absurd” by Western diplomats, according to the Wall Street Journal.

Other than the talk in Washington about arms supplies, the West has given Mr. Putin no incentive to drop his new offensive, which appears aimed at expanding the territory held by Russian proxies to the point where it can become a de facto statelet, like those Moscow has set up in occupied areas of Georgia and Moldova. European Union leaders and the Obama administration have discussed new sanctions, but so far those have been limited to individuals. Steps that might inflict significant further damage to the battered Russian economy, such as the exclusion of its banks from an international payment system, remain off the table.

Ms. Merkel is, meanwhile, arguing against any arms supplies for the besieged Ukrainian military, which, as a report released this week documented, lacks working antitank weapons or anti-artillery radar that could blunt the new offensive. Like some in Washington, Germany argues that U.S. arms supplies would simply lead to another escalation by Russia and more intense fighting — and that anyway, there is “no military solution” to the Ukrainian crisis. The logic seems to be that only Russia is allowed to pursue its aims by force — or that a military response to military aggression should be avoided as it would provoke the aggressor.

Ms. Merkel protests that she wouldn’t dream of going “behind the back of another country . . . and start questioning its territorial integrity.” German diplomats say they hope that her diplomacy will prompt Ukrainian President Petro Poroshenko and Mr. Putin to agree on a settlement. Yet to push Mr. Poroshenko toward such an accord while denying him the means to resist an invasion gives him few alternatives other than to capitulate to the Kremlin.

There’s nothing wrong in talking with Mr. Putin, provided that the West’s message is clear. Russia should be required to withdraw all its forces and equipment from Ukraine, reestablish the border under international monitoring and cease its support for a separatist statelet — or face a significant escalation of economic sanctions and a Ukrainian army with better weapons.