This piece was updated late Feb. 18.

The Feb. 12 Minsk II Ukrainian ceasefire agreement brokered by German Chancellor Angela Merkel is a fragile arrangement. Most analysts hold modest expectations. The past few days are proving them right.

Separatist and Russian forces continued their attack on Ukrainian forces at Debaltseve — despite the ceasefire that supposedly took effect on Saturday — and captured the town on Wednesday. Meanwhile Russian President Vladimir Putin’s spokesman has claimed that Moscow is not part of the conflict or the agreement.

President Barack Obama and other Western leaders continue to hope that the ceasefire will take hold. Yet it is harder to believe that the agreement will last than was the case last week. If Minsk II unravels, as did the first Minsk ceasefire of last September, pressure will likely grow on the White House to provide greater military assistance — including defensive arms — to Ukraine.

I joined with seven other former U.S. officials two weeks ago to advocate that Washington needed to provide significant military assistance to Ukraine. Our report, Preserving Ukraine’s Independence; Resisting Russian Aggression: What the United States and NATO Must Do, explained that most of this assistance would be nonlethal, such as radars to pinpoint the origin of enemy rocket and artillery fire. But with one major exception: light anti-armor weapons to help the Ukrainians confront the tanks and other armored vehicles that Moscow has poured into eastern Ukraine. The Ukrainian army could have put those weapons to good use at Debaltseve.

Such military assistance would fulfill Washington’s commitment to Ukraine under the 1994 Budapest Memorandum on Security Assurances — a key part of the arrangement under which Ukraine agreed to give up the world’s third-largest nuclear arsenal. The specific goal would be to increase the Ukrainian army’s ability to defend against Russian attack and, by raising the costs of aggression, dissuade Moscow from further fighting. The point now is to encourage the Kremlin to seriously seek a negotiated political settlement.

Over the past two weeks, Secretary of State John Kerry has reportedly told members of Congress that he supports arming Ukraine, something that Defense Secretary Ashton Carter endorsed during his recent Senate confirmation hearing. Obama, however, has thus far taken a cautious approach.

This is not a “slam-dunk” decision. It’s a 60 percent-40 percent or even 55 percent-45 percent call. But inaction presents more risks than assisting Ukraine’s military.

First is the real possibility that the fighting and bloodshed will go on. Though the Russian army has reportedly suffered hundreds of casualties, something the Kremlin has taken great pains to hide from the Russian people, it fights on. Moscow apparently considers the cost of this conflict sustainable.

Second, to the extent that Moscow concludes that the hybrid warfare it has carried out in Ukraine is a successful tactic, it may well be tempted to apply it elsewhere. The Kremlin claims a right to defend ethnic Russians and Russian speakers wherever they live and whatever their citizenship. What happens if Moscow were to try hybrid warfare in Estonia or Latvia, in “defense” of the ethnic Russian populations there? Those countries are members of the North Atlantic Treaty Organization that the United States has an obligation to defend.

Critics of providing defensive arms have offered a number of reasons why Washington should not do it. Let’s consider their main arguments.

Some assert that arming Ukraine would launch an inexorable slide culminating in U.S.-Russia war — even a nuclear conflict. Why? Providing anti-armor weapons does not automatically mean providing F-16s or the 82nd Airborne. Our report did not recommend U.S. troops, and the Ukrainians did not ask for them. Kiev also did not ask for offensive weapons. The Ukrainian army is hardly likely to march on Russia led by man-portable antitank missiles.

Washington can calibrate and control the level of military assistance. The limits should be made clear with Kiev in private, but the U.S. government can assuredly build in the necessary firebreaks on American involvement.

Critics also worry that, if the United States provides defensive arms to Ukraine, Russia would escalate. They argue that Russia cares more about Ukraine than does the West. Which is true. But those critics usually omit a key factor in the equation: Ukraine.

It is not just an object in a Russia-West tug of war. Ukraine gets a say and appears to care every bit as much — and more — about its own future.

Critics assume, moreover, that escalation would be an easy call for the Kremlin. It might not be that simple. Escalation would almost certainly require more overt involvement by regular Russian army units in a way that would be difficult for Moscow to hide or deny.

That raises problems for the Kremlin and Putin. Opinion polls show that most Russians do not want their army fighting in Ukraine. The more they see of the conflict, and the more casualties that result, the more likely that their support for Putin’s war would erode.

The Russian president does not appear to care much about dead Russian soldiers. But he does care a great deal about their impact on his public standing.

More overt Russian army involvement also would be more visible to the outside world. That would only bolster support in Europe and elsewhere for maintaining sanctions and adding more biting measures that would further damage the Russian economy.

Other critics claim that providing Ukraine defensive arms would end the cooperation that has developed between the United States and Europe. They can offer no evidence to support this, however. Merkel does not favor supplying arms, but she had ample opportunity during her Feb. 9 Washington visit to warn that doing so would disrupt transatlantic unity. She did not.

Some NATO allies, moreover, would likely provide arms to Ukraine if Washington did so. They include Poland, the Baltic states, Canada and perhaps Britain. British Foreign Secretary Philip Hammond last week ruled out arms “for the time being.” But he also suggested that Britain would not sit by as the Ukrainian army collapsed.

Providing military assistance and defensive arms to Ukraine is not risk free. But if Minsk II falls apart and the fighting grows, that would engender major risks as well — not only to Ukraine, but to other Russian neighbors if Moscow sees hybrid warfare as a winning tactic.

The provision of military assistance is not intended as a stand-alone policy. It is a piece of an overall strategy that consists of Western financial support to sustain Ukraine (provided that Kiev can pursue serious economic reforms) and economic sanctions on Russia designed to effect a change in Moscow’s policy toward Ukraine. By taking from Russia the military option, or the inexpensive military option, arming Ukraine aims, like sanctions, to get the Kremlin to seriously seek a political settlement.

Holding open the prospect of a political settlement that can address Russian and Ukrainian interests is the last key piece of the strategy. A settlement, however, needs a willing Russian partner prepared to accept a reasonable outcome. Putin tried to play the statesman in Minsk. As his army assists separatists in taking Debaltseve and Minsk II appears to unravel, what’s left of any confidence in his good faith comes increasingly into question.

Obama should now consider providing Ukraine more military assistance and defensive arms, with the goal of turning Moscow back to the real effort at finding peace. Though that action carries risks, inaction presents a more hazardous course.