As the war between Ukraine and Russia drags on, it is clear that Ukraine has mounted a far better resistance to Russian forces than many expected. To continue to do so, however, Ukraine will need more help from the West — and that brings with it a dangerous risk that the war could escalate to involve NATO.

Russia warned the West against sending further arms to Ukraine, saying such arms convoys could now be considered “legitimate targets” for the Russian armed forces.

Speaking to Russia’s Channel One broadcaster on Saturday, Russia’s Deputy Foreign Minister Sergey Ryabkov issued a warning to the West that could lead to a direct confrontation between Russia and NATO.

“We warned the United States that pumping Ukraine with weapons from a number of countries orchestrated by them is not just a dangerous move, but an action that turns the corresponding convoys into legitimate targets,” the deputy minister said, according to comments reported by Russia’s state news agency TASS.

Ryabkov said there could be consequences to what he called the West’s “thoughtless transfer” to Kyiv of weapons such as portable anti-aircraft missile systems and anti-tank missile systems, both of which have been supplied to Ukraine by several NATO members including the U.S. and U.K.

Close observers of Russia, and its ongoing invasion of Ukraine, expressed shock and dismay at Ryabkov’s comments.

“If Russia attacks Western arms shipments … it takes the conflict to a new level, of NATO vs. Russia,” Timothy Ash, senior emerging markets sovereign strategist at BlueBay Asset Management, said on Saturday, adding that a “critical moment in this conflict [is] coming up.”

“Does the West really realize the threat to our very system of government, and our way of life, from Putin, and is it willing to act,” he asked.

Despite Russia’s latest threats, the West is in a tricky position over Ukraine because its continued support for Ukraine in terms of arms, intelligence and financial aid, defense experts and strategists argue, could make or break Ukraine’s resistance and could even tilt the war’s outcome in Ukraine’s favor, something that seemed unimaginable when Russia invaded over two weeks ago.

“There can be a point where this balance [in the war] is shifted in favor of Ukraine,” Wojciech Lorenz, a senior analyst at the International Security Programme at The Polish Institute of International Affairs, told CNBC.

Additional support from NATO’s individual members in the form of arms shipments, intelligence and other forms of aid “really makes a difference and is why Russia is doing so badly,” he said.

There could even come a point, he added, where Ukraine is able to not only resist Russian forces but can launch counter-offensives against them “and reclaim lost territory.”

While Ukraine has won the affection of people and governments around the world for its brave stand against Russia’s invasion, Russia has been heavily sanctioned, making it geopolitically, economically and financially isolated and vulnerable.

With the World Bank’s chief economist predicting that Russia is edging toward a default on its foreign debt while at home, numerous foreign brands have pulled out of Russia or ceased operations there, and Russian consumers are feeling the pain of the central bank’s interest rate hike to 20% to bolster the crumbling ruble.

Aside from sanctions, which came swiftly and in a surprisingly unified way by the West, one of the biggest dilemmas for the West is how much military assistance it could and should extend to Ukraine. Ukraine is not a NATO member, but it is a pro-Western ally that’s geopolitically important as a buffer state between Russia and the rest of Europe.

NATO has repeatedly said that it stands by Ukraine and its leadership under President Volodymyr Zelenskyy, and NATO countries have unilaterally offered and delivered weaponry to Ukraine to help it defend itself.

However, Ukrainian officials have repeatedly called on Western officials to provide more support. This ranges from more actionable maneuvers — such as imposing the full weight of sanctions on Russia and providing more arms — to the more problematic plea for a “no-fly zone” over Ukraine. NATO has rejected the latter request, saying this could bring it into direct confrontation with Russia.

Without that extra support from NATO, strategists said, Zelenskyy needs to keep Ukraine at the forefront of the world’s geopolitical priorities, and to maintain other forms of support for the country.

“At this critical juncture, every significant weapons shipment he [Zelenskyy] receives, every word of support he receives and every action NATO takes helps him and help Ukraine and he’s trying to keep that squarely in the political view,” Ian Lesser, vice president of the German Marshall Fund of the United States, told CNBC on Thursday.

Describing Russia’s invasion and military aggression against Ukraine as “outrageous,” Lesser said it was still vital to keep up the momentum of support for the country, be it through emotional support which people around the world can give, or media coverage. However, he questioned how long such support could be sustained.

“There is already a shift in the discussion towards energy security, the cost to Western publics and economies, the stability of the international financial system. These are all very real issues of course but from Zelenskyy’s point of view, these are all distractions from the principal problem which is the fate of his people in Ukraine.”

Crucially, Lesser said, Western partners would be more inclined to keep up their support of Ukraine if they “believe that Ukraine can make good use of it.”

While Ukraine has a fighting chance of defeating Russia, analysts said that if the converse happens, President Vladimir Putin could be emboldened to attack NATO.

“Russia wants to change the security architecture in Europe, and wants to recreate the empire by taking control of Belarus and Ukraine at a minimum, so even if they aren’t able to achieve their goals now after a few years of reorganization they will try again,” senior analyst Lorenz said.

Lorenz said Putin’s intentions in this regard were made clear last December when Russia issued demands to the U.S. and NATO that it wanted legal guarantees ruling out NATO’s eastward expansion and the deployment of weapons that, as Putin said in early December, “threaten us in close vicinity to Russian territory.”

“Russia just needs to be strategically defeated,” Lorenz said, because if Putin feels that he has “achieved a victory by further undermining the territorial integrity of Ukraine, or the West forces Ukraine to accept some humiliating peace conditions like the recognition of the annexation of Crimea or the independence of Donetsk and Luhansk, then it will only mean that in a couple of years we’ll have war between Russia and NATO.”

Russia’s aggression in warfare appears to be becoming more indiscriminate, with its forces attacking a children’s hospital and maternity ward on Wednesday. Russia said it had not targeted civilians at the hospital, despite images indicating civilians were caught up in the attack, while Ukraine accused it again of committing a war crime.

There are concerns that Russia might resort to using biological warfare against Ukraine, with intelligence officials fearing that Russia could invent a pretext to use chemical, or even nuclear, weapons either against Ukraine, or any other nation if Russia feels directly confronted.

At the start of Russia’s invasion on Feb. 24, Putin warned Western nations that any interference in what he called Russia’s “special military operation” in Ukraine would be met with “consequences greater than any you have faced in history.” He did not provide details on what that would entail.

Most analysts agree that NATO’s current path of allowing member states to help Ukraine individually, while holding off on any collective measures, is the right one. But if Russia’s assaults on Ukraine take a darker turn, such a stance could be harder to maintain.

“NATO allies are appropriately concerned about the potential for a military escalation that could lead to a wider war between NATO and Russia,” Charles Kupchan, senior fellow at the Council on Foreign Relations, told CNBC Wednesday, although he praised the alliance’s “impressive steps” so far to provide military support to Ukraine.

“Such support is helping Ukrainians resist Russia’s invasion, and Ukraine’s military, its democratic government, and the country’s citizens have demonstrated defiant resilience,” he said.

Just how far Russia would — or could — go to retaliate against any nation helping Ukraine is uncertain, with analysts saying Putin’s increasingly reckless and unpredictable behavior makes it hard to judge.

“Considering where Russia currently stands, the potential for retaliation is currently limited — basically, Russia can’t afford to retaliate beyond provocation and scaremongering,” Anton Barbashin, a political analyst and editorial director of the journal Riddle Russia, told CNBC on Wednesday. He added that Russia would be hard-pressed to act, given that it’s tied up in Ukraine.

Cc:  CNBC