"Today, Moscow exploits the lack of any naval deterrence."

The relatively weak Western response to a Russian attack on Ukrainian navy boats in the Kerch Strait means that Vladimir Putin has gained a tactical advantage, which makes it more likely that Moscow will escalate further in the future.

It would be easy to dismiss the latest flare-up as Ukraine’s problem, but that would be foolish, ex-U.S. Ambassador to Ukraine John Herbst wrote for the Atlantic Council.

The Kremlin is pursuing a revisionist policy designed to weaken NATO and the European Union, while its current aggression is focused on Ukraine.

The smartest way for the United States to thwart Putin’s efforts is to make him pay a heavy price for his war against Ukraine, Herbst believes, adding that this can be done at a very low cost to the U.S.: sanctions on Russian leaders and the economy and weapons for Ukraine.

The ex-envoy, who is now a director of the Eurasia Center at the Atlantic Council, has named weapons the United States should provide to shore up Ukraine’s vulnerabilities.

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"We should provide at least six, and as many as twelve, Mark V PT boats. They should be equipped with at least fifty and as many as 100 Hellfire missiles. The United States should also provide at least 100 Harpoon anti-ship missiles. Mark V’s can be transported by air to Mariupol and Berdyansk, Ukraine’s two port cities in the Sea of Azov, where Russia fired on Ukrainian boats on November 25," the op-ed reads.

Harpoons have a range of over fifty miles and would be a problem for Russian ships approaching Mariupol or Berdyansk and for any amphibious operation against Ukraine’s coast, whether in Azov or the Black Sea.

Given that the Ukrainian navy cannot match Russian firepower in the Sea of Azov, fast Mark V patrol boats would provide a punch that would put larger Russian vessels at risk. The Mark V’s carry torpedoes and the United States could make the boats much more of a threat to the Russian navy by providing nautical Hellfire missiles, which can be launched from the Mark V.

"Finally, we should also provide the radar and intel systems that would help Ukraine’s military keep track of the Russian navy in the Sea of Azov. This would be essential to gauge the threat of that navy and would be important for targeting those ships," John Herbst wrote, adding that this is "not to encourage Ukraine to shoot at the Russian navy, but to give it the capability to shoot back once provoked, which would establish a measure of deterrence in the Sea of Azov."

"Today, Moscow exploits the lack of any naval deterrence," the ex-ambassador stressed.

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The Kremlin has established overwhelming military superiority in the Sea of Azov and, with their attack on and seizure of Ukrainian navy vessels in late November, have demonstrated that they want no challenge from Ukraine there.

Since April, Moscow has used this predominance to harass shipping to and from Ukraine’s Azov ports, drastically reducing shipping. At the same time, its naval presence also gives Moscow the ability to conduct amphibious military operations against Ukraine’s Azov coastline.

"The United States is not in a position to offset Moscow’s naval superiority in the Sea of Azov, just as it is not in a position to offset the Kremlin’s conventional superiority in the war in Donbas. But the United States could give Ukraine assets to provide an asymmetric challenge to Moscow in the Sea of Azov," Herbst wrote. "This would be similar in some ways to the US provision of Javelins to Ukraine, which did much to neuter Moscow’s tank advantage in the Donbas and convince Kyiv that the US position remains firm."

In conclusion, the former envoy notes that the U.S. response to Moscow’s escalation in late November has been underwhelming, which Putin is likely to interpret "as a green light if we do nothing but cancel meetings."

"Putin is a menace to the international order and he’s only getting bolder," says the expert. "Now is the time to act."