There is a new proposal to send arms to Ukraine:

The U.S. Pentagon and State Department have devised plans to supply Ukraine with antitank missiles and other weaponry and are seeking White House approval, U.S. officials said, as Kiev battles Russia-backed separatists and ties between Moscow and Washington fray.

American military officials and diplomats say the arms, which they characterized as defensive, are meant to deter aggressive actions by Moscow, which the U.S. and others say has provided tanks and other sophisticated armaments as well as military advisers to rebels fighting the Kiev government.

Arming Ukraine remains a bad, foolish idea for all the reasons I have given before. Advocates of sending weapons say that it will serve as a deterrent, but it will almost certainly be perceived as a provocation by Moscow and could easily serve as a pretext for more aggressive behavior from Russia and its proxies. Ukraine will not be made more secure by doing this, and the U.S. has no obligation to help defend Ukraine in any case, but the bigger problem with the proposal is that it has nothing to do with promoting U.S. or allied security. Some of our most important European allies, including Germany and France, understand this, and have opposed the same idea in the past.

Sending more weapons into Ukraine risks reigniting and escalating the conflict at the same time that it deepens U.S. involvement in it. It would antagonize Russia while further entangling the U.S. in a conflict in which we have no vital interests. If Russia responds in kind or with an even more aggressive response, the U.S. can’t credibly threaten to counter them because Ukraine will always matter far more to them than it does to us. The White House should reject the latest misguided proposal to send arms to Ukraine.

P.S. Leonid Bershidsky spells out why sending weapons to Ukraine is also unnecessary:

Two years after both sides have largely kept to existing demarcation lines (minor encroachments aside), it is militarily unnecessary to provide Ukraine with lethal weapons unless the U.S. wants to encourage it to try to reclaim the “people’s republics.” That would be a mistake. Though Russia doesn’t have enough resources to take over and hold Ukraine while still staying on the lookout for other military threats, it has plenty of money, firepower and determination to defend the separatist statelets.