It should be a familiar routine by now: Vladimir Putin offers an apparent diplomatic breakthrough in eastern Ukraine. Western negotiators get overexcited; the peace-shuttling commences; an agreement is signed. But the Russian strongman only uses the process to consolidate his gains on the ground, without making good on his commitments. Then he pounces for more territory when conditions are advantageous.

The Kremlin’s call for deploying a United Nations peacekeeping force to eastern Ukraine is an example of this familiar ruse, and the West should avoid falling for it.

The Russian president raised the idea at a news conference in China on Tuesday, and Moscow formally presented the proposal to the U.N. Security Council later the same day. It would involve dispatching lightly-armed U.N. troops to protect international observers who monitor the implementation of the so-called Minsk Agreements aimed at de-escalating the conflict in eastern Ukraine. The Ukrainian government has previously called for U.N. peacekeepers, as well, so Russia’s apparent embrace of a blue-helmet solution raised eyebrows.

German Foreign Minister Sigmar Gabriel said he was “very pleased” to see that Putin “wants to further discuss a demand which Russia had rejected in the past.” Moscow, he added, “had effected a change in its politics that we shouldn’t gamble away.” The U.S. State Department also welcomed the move, though its response was more cautious, noting that “any such force should have a broad mandate for peace and security throughout the occupied territory in Ukraine.”

Therein lies the catch. Moscow wants the peacekeepers to be deployed only to the so-called line of contact separating Ukrainian troops and Russian-backed “rebels” (they are, in fact, a Russian occupation force). The Kiev government insists–rightly–that the peacekeepers be deployed throughout the conflict zone, and especially to the Russian-Ukrainian border.

If Russia had upheld its end of the Minsk Agreements, Ukraine would have regained control of its own border months ago. As it is, Putin continues to control the border and transfer troops, advisors, and materiel to Russian proxies, in violation of Minsk. Deploying blue helmets to the contact line but not to the border would allow Moscow to further deepen and entrench its position in eastern Ukraine. It could even lend Russia’s de facto occupation an air of international legitimacy, since it would be foreign troops monitoring the pseudo-border of the contact line.

The timing of Putin’s proposal is another red flag, seeing as it comes amid reports that the Trump administration is considering supplying defensive weapons to Ukraine, including crucial Javelin antitank missiles. (President Obama refused to arm Kiev–something to remember when you see Obama-administration alumni posture as die-hard Cold Warriors on TV these days.) By calling for U.N. intervention now, Putin may be trying to raise the diplomatic price the U.S. has to pay for arming Ukraine. Yet the the price of falling into Russia’s trap is higher, since failing to deter aggression today invites more of it tomorrow.