NATO’s top military commander told United States lawmakers that even if the U.S. armed Ukraine’s army, they wouldn’t be able to stop the Russians from expanding further into Eastern Ukraine.

“In the current configuration I do not think that Ukrainian forces can stop a Russian advance in Eastern Ukraine,” NATO Commander Gen. Philip Breedlove said during a House Armed Services hearing Wednesday on the Pentagon’s response to Russian aggression on NATO’s eastern flank. “And to the degree that we can supply help, I’m not sure that they could stop a Russian advance in Eastern Ukraine even if we supply aid … but what we’re doing now is not changing the results on the ground.”

“More than 1,000 pieces of Russian military equipment have been transferred into Ukraine, including tanks, armored personnel carriers, heavy artillery pieces and other military vehicles and equipment,” he said. “These are not the actions of a good faith negotiating partner.”

I think first and foremost, Mr. Putin has not accomplished his objectives in Ukraine, so next is probably more action in Ukraine. Gen. Philip Breedlove, NATO's supreme allied commander for Europe

Some lawmakers and former Obama administration officials have been eager to arm Ukraine’s military in the wake of Russia’s annexation of Crimea, and a number of members of Congress have introduced legislation to that effect. Meanwhile, fighting between Kiev’s military—largely gutted by years of corruption—and pro-Russian separatists has continued for nearly a year now, despite the two sides already signing two ceasefires, the so-called Minsk-1 and Minsk-2 agreements.

Sen. John McCain, R-Ariz., said Wednesday on the Senate floor that the U.S. is obligated to arm Ukraine, regardless. “To me, it’s the most unbelievable view that somehow we don’t want to provoke Vladimir Putin, who has taken Crimea—they’ve written that off. Shot down an airplane, at least with Russian equipment. Moved and dislocated Eastern Ukraine. Caused an economic crisis. And we don’t want to provoke Vladimir Putin?”

House lawmakers, too, remained skeptical of any lasting ceasefire. But they were also at a loss for what to advise, given Breedlove’s admitted inability to predict how Russian President Vladimir Putin would respond to a lethally armed Ukrainian military.

“We have to be absolutely straightforward to say that none of us knows what Mr. Putin will decide,” he said. “If we take action, many believe he may accelerate. If we take action, others believe it may raise the cost to him.”

(Read more: Ukraine’s Military Needs More Than Just Arms)

“We’ll have Minsk 3, Minsk 4 and Minsk 5 and still no action out of Russia,” Rep. Rick Larsen, D-Wash., said.

Breedlove seemed to agree. “I think first and foremost, Mr. Putin has not accomplished his objectives in Ukraine, so next is probably more action in Ukraine,” he said. "What is clear is that right now it is not getting better, it is getting worse every day."

The Ukrainian Defense Ministry said Wednesday that there have been “over 430 artillery, Grad [rocket], tank and small arms attacks against the Ukrainian positions and civilians” between Feb. 15 and 24. However, Ukrainian officials also said Tuesday marked the first day since the ceasefire was signed on Feb. 12 that none of its soldiers were killed—though one was injured—from shelling on the front lines.

What is clear is that right now it is not getting better, it is getting worse every day. Gen. Breedlove

Breedlove said U.S. and NATO strategy should continue leveraging diplomatic, information, military and economic means to help allies alter Russia’s course. This includes additional economic sanctions; but also training for allied nations in order for them to recognize the first signs of Russia’s use of unconventional warfare mixing deception, cyber attacks, regular forces and economic intimidation. The most likely future targets in that respect remain Eastern Moldova and Transnistria, Breedlove explained, as well as the Georgian breakaway region of Abhkazia—since all contain ethnic Russian populations like Crimea. That means from nearly every angle, Breedlove said, the U.S. and Europe will have to ratchet up the costs to Putin “in his internal environment more than the external environment.”

“You’re talking body bags?” committee member Rep. Mike Rogers, R-Ala., interrupted Breedlove.

“That’s right,” he said. “I think we should talk about raising the cost for Russia in many dimensions.”

Asked at an afternoon briefing at the Pentagon if there is a “red line” for continued Russian aggression before NATO would act, Breedlove said flatly, “No,” though he expressed concern about Russian rocket systems in Crimea that could easily involve nuclear weapons without the alliance’s knowledge.

“This is very worrisome,” Breedlove said. “Ground-based weapons systems that are typically conventional which a nuclear capability could be fielded on. Or dual-use aircraft in the Crimea that could either be nuclear or conventional… This dual-use capability brings an ambiguity that is really hard for us to pick up in our intelligence and indications and warnings.”

With shelling in Ukraine still being reported this week, the reality is the body bags could continue to mount—a toll that’s already topped 5,000, according to the U.N.—for both Kiev and the separatists. Already this week, both the United Kingdom and Poland announced they would send military advisors to Ukraine for a variety of tasks, including infantry and intelligence training. U.S. paratroopers are expected to begin training four companies of Ukrainian national guard soldiers, Lt. Gen. Ben Hodges, commander of U.S. Army Europe, said during his first visit to Kiev in late January. Those troops, drawn from the Army's 173rd Airborne Brigade Combat Team, based out of Vicenza, Italy, are set to operate about 40 miles from the Polish border in Ukraine’s Yavoriv Training area starting mid-March.