In response to threats from NATO that it will be expanding its military capabilities eastward, Russia on Tuesday countered by saying such moves will only result in military recalibrations of its own.

Ahead of a NATO summit scheduled for later this week and citing repeated announcements by NATO Secretary-General Anders Fogh Rasmussen that a new military "spearhead"— a 4,000-soldier "rapid response" fighting force—would be positioned in eastern Europe, high-ranking Russian officials were pushing back.

Public Chamber deputy secretary Sergei Ordzhonikidze, told a state news agency that Rasmussen's plans amounted to "military hysteria" and betrayed historic promises. He said Russia's only option would be to respond with "reciprocal measures" of its own.

“When NATO troops are approaching our borders, of course, we develop a plan," said Ordzhonikidze. "It is a threat when troops are being stationed next to your border. I recall NATO’s commitment not to expand the bloc’s territory eastward … All that remains to us is to somehow oppose this expansion of NATO.”

Rasmussen first publicly presented the idea for NATO's eastward expansion last week during a sit-down interview with European newspapers. Strikingly, those reports came out just as Russian President Vladimir Putin and Ukrainian President Petro Poroshenko were sitting down in Minsk, Belarus for their first face-to-face meeting over the deadly crisis in Ukraine. The timing of Rasmussen's comments was not lost on Russian Foreign Minister Sergei Lavrov.

“There is one very interesting fact," Lavrov said Tuesday during a live TV interview, "that this [NATO] initiative appeared right after the meeting in Minsk where agreements on the process of the Contact Group were trying to find a commonly acceptable decision on the current domestic crisis in Ukraine.”

Lavrov categorized U.S. statements and Rasmussen's talk of NATO expansion as a conscious effort to undermine fragile peace efforts now underway between the Ukrainian rebels in the east and leaders of the Kiev government.

“It’s quite unfortunate that such moods in strengthening the positions of the ‘war party’ are actively warmed up and urged on out of Washington and several European capitals, and more and more often out of Brussels and from the NATO Headquarters where the secretary-general of the North Atlantic Alliance with or without reason comes out with announcements that do not fall under his jurisdiction,” Lavrov said.

In separate comments, Russian Security Council deputy secretary Mikhail Popov told RIA Novosti that in response to NATO's push to expand, plans are now underway to make changes to Russia's military doctrine "triggered by geopolitical factors, including NATO’s activities next to Russian borders and the situation in Ukraine."

U.S. President Barack Obama leaves for Europe this week and will travel to Estonia—a former Soviet bloc state but now a member of the NATO alliance alongside neighboring Latvia and nearby Lithuania—before joining other NATO leaders in Wales for the summit on Thursday.

Obama's stop in Estonia is seen as a symbolic show of force towards Moscow, which sees NATO incorporation of Estonia and the other Baltic countries as one of the original betrayals of the western military alliance. President Vladimir Putin has previously stated that an increased military footprint so close to its borders—given 20th Century history—would be interpreted as a threat to his nation's continued security. Last week, Putin had harsh words for the Kiev government and western leaders as he reminded the world that Russia is a nuclear power that would defend its interests in the region.

And according to the New York Times:

On Tuesday morning, an aide to President Vladimir V. Putin of Russia played down but did not deny a report that Mr. Putin had told José Manuel Barroso, president of the European Commission, “if I want, I will take Kiev in two weeks.” The comments came as Mr. Barroso asked Mr. Putin about Russian troops in Ukraine. Mr. Putin, who has repeatedly denied having any troops there, then turned “to threats,” Mr. Barroso told the Italian newspaper La Repubblica. Yuri V. Ushakov, an aide to Mr. Putin, said Mr. Barroso’s recounting of a private conversation was “inappropriate.” “Whether these words were said or not, in my viewpoint, this quote given is taken out of context and it had absolutely different sense,” Mr. Ushakov said. On a nationally televised call-in show in April, Mr. Putin said, “When the infrastructure of a military bloc approaches our borders, we have grounds for certain apprehensions and questions.”

Whatever the accurate details of the conversation between Putin and Barroso may be, the explicit threat now on the table is that if the Ukraine crisis cannot be contained and if NATO pushes to accept Ukraine into its sphere while expanding military operations eastward, experts warn the ingredients exist not only for a new and heightened Cold War, but an actual armed conflict between Russian forces and NATO-aligned countries—something not seen since the end of World War II.

According to a recent essay by independent journalist and analyst Eric Margolis:

... any military clash in Ukraine would initially be limited in scope and intensity. But a confrontation could quickly escalate into a dangerous crisis. The Cold War taught that nuclear –armed powers must never fight directly, only through proxies. Nothing is worth the risk of nuclear war, even a limited one. Let the Ukrainians sort out their differences by referendum. On the 100th anniversary of World War I, we again see our leaders playing with matches.

And as Alice Slater, New York director of the Nuclear Age Peace Foundation, writes: