Russia appears to be preparing to test its new nuclear-armed, nuclear-powered cruise missile, according to two U.S. researchers and a Western security source, even as Russian President Vladimir Putin readies for talks on Ukraine with U.S. President Donald Trump on Friday.

Jeffrey Lewis of the California-based Middlebury Institute of International Studies, and Decker Eveleth of the CNA research and analysis organization, based in Virginia, reached their assessments separately by studying imagery taken in recent weeks until Tuesday by Planet Labs, a commercial satellite firm.

They agreed the photos showed extensive activity at the Pankovo test site on the Barents Sea archipelago of Novaya Zemlya, including increases in personnel and equipment and ships and aircraft associated with earlier tests of the 9M730 Burevestnik (Storm Petrel).

"We can see all of the activity at the test site, which is both huge amounts of supplies coming in to support operations and movement at the place where they actually launch the missile," Lewis said.

A Western security source, who asked not to be further identified, confirmed that Russia is preparing a Burevestnik test. Lewis said a test could occur this week, raising the possibility it could overshadow the Trump-Putin summit in Alaska.

Asked for comment, the White House did not address the possibility of a Burevestnik test.

The Pentagon, the CIA, and Russia's Defense Ministry declined to comment. Putin has said the weapon - dubbed the SSC-X-9 Skyfall by NATO - is "invincible" to current and future missile defenses, with an almost unlimited range and unpredictable flight path. Lewis, Eveleth, and two arms control experts said the missile's development has taken on more importance for Moscow since Trump announced in January the development of a U.S. Golden Dome missile defense shield.

But many experts say it is unclear the missile can evade defenses, will not give Moscow capabilities it does not already have, and will spew radiation along its flight path.

A test would have been scheduled long in advance of last week's announcement of the Trump-Putin meeting, the researchers and experts said.

But Putin could have suspended preparations in view of U.S. spy satellites to signal his openness to ending his war in Ukraine as well as to restarting arms-control talks with the U.S., the experts said. New START, the last U.S.-Russia pact capping strategic nuclear deployments, expires on February 5.

"Sometimes you can push up or push down the schedule for a political reason," said Tom Countryman, a former acting undersecretary of state for arms control.

The Burevestnik has a poor test record, according to the Nuclear Threat Initiative advocacy group, with two partial successes among 13 known tests.

Special aircraft

Eveleth and Lewis said the Planet Labs imagery showed stacks of shipping containers, equipment, and personnel arriving since late July.

Lewis said two aircraft equipped to gather test data had been parked at the archipelago's Rogachevo military airfield since mid-July. Images he provided to Reuters showed two large jets mounted with saucer-shaped radar domes.

He noted the presence of at least five ships associated with previous tests. A ship-tracking website - VesselFinder.com - showed a sixth ship linked to earlier tests was due to arrive on Tuesday, he said.

Reuters confirmed the website showed the vessel, a cargo ship named the Teriberka, bound for Novaya Zemlya, but could not independently confirm the researchers' other findings.

Eveleth and Lewis said they began examining imagery of Pankovo starting from July, after Russia on August 6 published a notice to mariners to stay away from the area from August 9-12.

Reuters found a series of notices on the U.S. Federal Aviation Administration's Defense Internet NOTAM Service issued by Russia showing a possible launch window between August 9-22.

The Norwegian military told Reuters in an email that the Barents Sea is a "prime location for Russian missile tests" and that it had indications from notices and maritime warnings of "preparations for test activities."

But it said it would "not confirm any knowledge of what kind of munitions they are to test."

In late July, Eveleth said, he noticed a shelter protecting the Burevestnik launcher from the weather was being slid back and forth, which he called "very clear evidence" of plans for a test.

Lewis provided to Reuters images taken of the site on August 7 showing the protective launcher cover, stacks of shipping containers, a crane for moving them, and a helicopter.

"It's full steam ahead," he said of the pace of test preparations.