Suddenly, Russian President Vladimir Putin is talking about a U.N. peacekeeping mission in the conflict he is nursing with Ukraine in the eastern Donbas region. Why? Previously, Russia has been firmly against any U.N. involvement, not to mention international peacekeepers. Something has changed for the Kremlin.

To be sure, the version of the peacekeeping mission Putin proposes is a distinct non-starter. He wants a light force along the contact line between his separatist forces and the rest of Ukraine. That casts the conflict as an internal Ukraine affair, providing cover for Russia’s forces there as well as for its control of the international border.

I doubt even China would buy this. On the present Security Council, possibly Bolivia would support Putin’s plan, but that’s it.

Still, Putin’s stance is still an interesting change and opens up room for a debate about a real peacekeeping mission to implement the moribund Minsk peace agreement, which was supposed to resolve the conflict. Certainly not today, perhaps not even tomorrow, but possibly the day thereafter.

The Kremlin is evidently deeply disturbed by reports that the Trump administration is seriously contemplating supplying Ukraine with modern defensive weapons. This would greatly complicate any future Russian option to strike Ukraine with its regular military forces, as it did in August 2014 and February 2015. These types of military strikes are clearly seen by the Kremlin as key to its management of the conflict. Without this option, I suspect Putin would fear being on a slow slide toward losing Russia’s position in Ukraine entirely.

The Trump administration should certainly go ahead with the arms supplies — why should Ukraine be denied the right to defend itself? But the United States and European Union should simultaneously take up the issue of peacekeeping. They should call Putin’s bluff and put on the table proposals for a robust peacekeeping mission to implement the Minsk agreement, which calls for elections in the occupied territories, the withdrawal of Russian forces and the return to Ukraine of control over its border.

There is a precedent. A robust U.N. mission took over a Serb-separatist part of Croatia, disarmed it, put governance in order and gradually restored respect for the international border between Serbia and Croatia. It wasn’t perfect in every respect, and the Donetsk and Luhansk separatist regions are much bigger. The task of economic revitalization is also of an order of magnitude larger. But in comparison with sorting out Afghanistan, trying to get Iraq to work or getting a new Syria up and running, it’s peanuts.

Nothing of this will be possible if the Kremlin isn’t interested in getting out of its deepening Ukraine quagmire, and I don’t think the Kremlin is there yet. But we have just seen the first small sign of something moving. The West should take it up and press forward with genuine peacekeeping options.

That Donbas needs peace is obvious. Already some 10,000 people have lost their lives in the conflict. And Ukraine needs peace to go forward with its democratic reforms. Eventually, so will Russia. It could be the key to not only a more cooperative relationship with the Wes, but also long-term reconciliation with a Ukraine that otherwise risks becoming an eternal enemy of Russia.