Russian strategic bombers conducted flights within the U.S. defense zone close to northern Alaska and the Aleutian Islands last week in Moscow’s latest incident of nuclear saber rattling against the United States, according to defense and military officials.

Two Bear H nuclear-capable bombers were detected flying into the military’s Alaska Air Defense Identification Zone (ADIZ) near the Aleutians, where a strategic missile defense radar is located, and Alaska’s North Slope region by the Arctic and Chukchi Seas on April 28 and 29, military officials told the Washington Free Beacon.

Lt. Cmdr. Bill Lewis, a spokesman with the U.S. Northern Command, confirmed the fighter intercept of the latest bomber incursion but declined to provide details.

"Two U.S. F-22's from Elmendorf Air Force Base, Alaska, were launched and visually identified Russian aircraft on the night of April 28, as the Russian Air Force flew standard out of area flights near Alaska," Lewis said.

The bombers did not enter U.S. airspace, he said.

However, the Alaska ADIZ is a formal national security zone used by the military to monitor both civilian and military aircraft. The dispatch of F-22s is an indication the bomber flights posed a potential threat to U.S. territory.

It was the fifth incident of Russian strategic bombers flying against the United States since June, when Bear bombers were intercepted near Alaska during a large-scale Russian strategic nuclear exercise that Russian military officials said involved practice strikes against U.S. missile defense sites in Alaska.

Less than a month later, on July 4, two more Bears flew the closest to the northern California coast that Russian aircraft have flown since the days of the Soviet Union.

Then in February two Bears circled Guam, a key U.S. military hub in the Pacific.

Additionally, Backfire strategic bombers flew simulated strikes against U.S. missile defenses and bases in Japan last month.

U.S. officials say the stepped-up Russian bomber flights are part of Moscow’s attempt to influence U.S. missile defense policies. Russia, along with China, for years opposed U.S. missile defense programs through propaganda and influence operations. Both states want the defenses curtailed to protect their strategic offensive missiles, which are currently being expanded.

The Pentagon in March announced it was adding 14 new long-range missile interceptors to the 30 ground-based interceptors based at Fort Greely, Alaska, and Vandenberg Air Force Base, Calif. Defense Secretary Chuck Hagel, in announcing the added interceptors, also said the Pentagon is canceling an advanced Navy SM-3 interceptor that was to be deployed in Europe and would be capable of shooting down long-range missiles from Iran.

The latest bomber incursion near Alaska also followed the April 14 visit to Moscow by National Security Adviser Thomas Donilon, who presented a letter from President Barack Obama to the Russians on missile defenses. Details of the letter to Russian President Vladimir Putin remain secret but Russian officials described it as containing a number of proposals "promoting dialogue and cooperations."

Obama was overheard on an open microphone in March 2012 telling then-Russian President Dmitri Medvedev that he would have "more flexibility" in dealing with Russia on missile defenses, an indication he is preparing to make further concessions limiting U.S. missile defenses in future talks.

Administration officials have said publicly there are no plans to limit U.S. missile defenses in the talks.

Moscow is demanding legally binding guarantees that U.S. missile defenses in Europe will not be used to target Russian offensive ballistic missiles.

U.S. officials said Obama appears to be preparing to make concessions to the Russians on missile defenses as a way to seek a new round of strategic arms cuts with Moscow. He is set to visit Russia in September when arms control is expected to be a major topic of discussion.

Northern Command did not announce the April 28 bomber incident and declined to release details on the latest flights as part of the Obama administration’s conciliatory policy of seeking to "reset" ties with Russia.

However, two days after the incident the command issued a press release highlighting its cooperation with the Russian military announcing plans for a joint U.S.-Russian flight exercise designed to counter hijacked aircraft.

The statement said Russian air force officials on April 27 completed talks with Northern Command officials at Peterson Air Force Base, Colo., on the next exercise dubbed Vigilant Eagle 2013.

The exercise will be held in August in Anchorage and at Anadyr, home of a major strategic bomber base in the Russian Far East where the string of bomber flights are believed by U.S. officials to have been launched.

The exercise "will focus on national procedures for monitoring the situation and the cooperative hand-off of a hijacked aircraft from one nation to the other while exchanging air tracking information."

The exercise series is "an extraordinary and historic opportunity for NORAD and the Russian Federation to coordinate on the response to a mutually acknowledged hijacking threat," said Joe Bonnet, director of joint training and exercises for NORAD and U.S. Northern Command. "From a participant’s perspective, it is more than a military exercise; it is creating lasting bonds and partnerships extremely valuable for the security of our nations."

The last exercise in August 2012 was a "computer-assisted" simulation. The next exercise will involve "live-fly" of aircraft.

"This year’s exercise will continue building and strengthening the cooperation and partnership established between the two countries," the statement said.

Some defense officials and military analysts are questioning why the command would seek to cooperate with the Russians at a time when Moscow is flying threatening bomber missions against the United States.

While the exact nature of the training mission flown by the Bear Hs during the April 28 flight is not known, one official said it was likely targeting practice against the Cobra Dane radar located on Shemya Island in the far western Aleutians. The North Slope flight was probably designed to signal that Russia is preparing to strike the Trans-Alaska Pipeline, the official said.

Retired Air Force Lt. Gen. Tom McInerney, a former Alaska Air Command commander, said: "The Russians continue to play the administration like a fiddle, sending signals that they still have a strategic air force and can project power while the U.S. continues to ground alert squadrons and unilateral disarms."

"Is this the administration’s idea of ‘reset relations’ with Russia?" he asked.

Retired Air Force Lt. Gen. Trey Obering, a former director of the Missile Defense Agency (MDA), told the Free Beacon last month after the Russian bomber practice against Asian missile defenses that the flights are a clear sign Moscow has no interest in cooperating with the United States on missile defenses.

"I engaged with the Russians regularly as MDA director to propose cooperation on missile defense," Obering said. "After I retired, I participated in a group led by [former National Security Adviser] Steve Hadley which proposed an architecture which would allow for cooperation without impinging on each nation's sovereignty and would prevent the disclosure of any sensitive technology or information. These efforts were met with Russian intransigence."

The Russian opposition and bomber flights mean Moscow will not cooperate with the United States in any meaningful way, Obering said.

As a result, he said, the United States should make no concessions to the Russians and instead should pursue U.S. national security interests in defending American territory and allies.