Two Russian strategic bomber jets reportedly practiced cruise missile attacks against targets in the United States during a training mission last week that defense officials said appeared to occur around the same time that the NATO summit in Wales was held on Thursday and Friday, according to a report in the Washington Free Beacon.

As part of a recent training mission, the pair of Russian Tu-95 Bear bombers were tracked flying over the Labrador Sea last week in the northern Atlantic Ocean near Iceland, Greenland and Canada's northeast.

Analysis of the flight indicated that the aircraft were conducting practice runs to a pre-determined "launch box" - an optimum point for firing nuclear-armed cruise missiles at U.S. targets, said defense officials familiar with intelligence reports, adding that each aircraft was capable of striking targets as far away as 1,800 miles since they were outfitted with six AS-15 nuclear-armed cruise missiles.

Although representatives for the U.S. Northern Command and Northern American Aerospace Defense Command, or NORAD, declined to comment on the bomber flights in the North Atlantic, they told RT.com in an email Monday afternoon that they could not confirm the allegations published by the Free Beacon.

However, neither the U.S. nor Canadian fighter jets were asked to intercept the alleged Bear-H bombers since the incident occurred outside the North American Air Defense Identification Zone.

Additional details of the incident that took place over the Labrador Sea, the stretch of the Atlantic between Greenland and Canada's Labrador Peninsula, could not be learned.

Meanwhile, "Google Earth analysis reveals that a Tu-95 launch box located in the Labrador Sea and firing AS-15 missiles would be in range of Ottawa, New York, Washington, and Chicago, and could reach as far south as the Norfolk Naval base," according to WFB.

"However, air-launched cruise missiles fired from that location and outside the air defense identification zone would be unable to reach Kings Bay, Georgia-the homeport for U.S. ballistic missile submarines and a key strategic nuclear target."

Last week, after officials from the U.S., Canada and other allied partners discussed the escalating crisis in eastern Ukraine and potential action that could be undertaken to counter perceived Russian aggression during the NATO summit, a Russian general called for Moscow to change its doctrine to include preemptive nuclear strikes on the United States and NATO last week, RT reported.

Gen. Yuri Yakubov, a senior Defense Ministry official, was quoted by the state-run Interfax news agency as saying that Russia's 2010 military doctrine should be revised to identify the United States and the NATO alliance as enemies and clearly outline the conditions for a preemptive nuclear strike against them.

Yakubov said among other needed doctrinal changes, "it is necessary to hash out the conditions under which Russia could carry out a preemptive strike with the Russian Strategic Rocket Forces," Moscow's nuclear forces.

Since Russia regards nuclear arsenal as the main element of its power status, it frequently issues public nuclear threats, said Mark Schneider, a former Pentagon strategic policymaker and current senior analyst at the National Institute for Public Policy.

"Putin began what he called bomber 'combat patrols' in 2007, and they continue," Schneider said. "They are designed to intimidate as well as practice nuclear bomber attacks."

Meanwhile, Admiral Cecil Haney, commander of the U.S. Strategic Command, which is in charge of nuclear forces, said last month that he is concerned both by large-scale Russian nuclear exercises and by increased bomber flights near the United States.

"Clearly, we at the U.S. Strategic Command do monitor the strategic environment," Haney said noting large-scale nuclear exercises during the Ukraine crisis.

"Any nation state has the right to train," he added. "It's just interesting how that information [on nuclear forces exercises] is readily available on YouTube. Clearly, the actions associated with Ukraine are problematic."