(NewsNation) — Russian foreign minister Sergey Lavrov stoked new fears of a nuclear war Tuesday when he said “the danger” of such a conflict “is serious.” However, a military expert said it is unlikely” Russia will use nuclear weapons.

Lavrov’s comments come just one week after he said Russia would not use nuclear weapons in an interview. And retired U.S. Marine Col. Mark Cancian, an expert on international military affairs, said Tuesday on NewsNation’s “Rush Hour” that Russia is not likely to deploy nuclear weapons at this stage in the war.

“The time to use them would have been during the siege of Kyiv, when they might have had a decisive battlefield advantage from using them,” Cancian said. “Now they’ve reduced their war aims and are focused on the East.”

Russia shifted the focus of its invasion of Ukraine to the eastern Donbas region, which is held mostly by pro-Russian separatists.

Cancian believes the new Russian strategy won’t warrant the use of nuclear weapons but he is not completely ruling them out of the realm of possibility.

“It’s unlikely they will use them unless we get in a situation where the Russian army maybe collapses, maybe the Ukrainians push into Russia-proper, then you could imagine the Russians using nuclear weapons,” Cancian said. “They do have a doctrine of using nuclear weapons to offset conventional weakness.”

As evidenced by the deployment of troops and anti-air defense weapons to NATO nations in Eastern Europe, Cancian believes the United States has taken the threat of Russian nuclear war seriously, saying “if the Russians were to try something, I think we are pretty well-prepared.”

“Russia has been rattling it’s nuclear saber from the very beginning of the conflict, threatening NATO and trying to keep NATO forces out of Ukraine, and mostly the United States and NATO have told Russia to stay out of NATO territory,” Cancian said. “I think both sides have come to an accommodation; we won’t go into Ukraine, they won’t strike into NATO even though we have bases that are supplying equipment and logistics to the Ukrainians.”

What Russia will continue to do however, is launch attacks on Ukrainian supply lines, especially to slow up the delivery of military supplies coming from the United States, Canada and other NATO countries.

NATO countries have continued deliveries of anti-aircraft stinger missiles, anti-tank weapons, armored vehicles, anti-ship weapons and troves of artillery guns and ammunition to Ukraine.

Stopping those weapons from reaching Ukrainian hands will be Russia’s most immediate objective.

“I think at this point, that is unlikely. The Russians have their hands full but what they are doing is they are using their missiles and their airpower to try and interject the flow of supplies once they get inside Ukraine,” Cancian said. “And that’s a fair military target.”