The comments by U.S. Air Force General Philip Breedlove on October 30 came the same day that Russia staged a major test of its strategic and tactical missile forces, firing multiple ballistic and cruise missiles at testing ranges throughout the country.
Breedlove told reporters at the Pentagon that Moscow continued to defy the so-called Minsk agreements that resulted in a cease-fire in eastern Ukraine's Donbas region.
He said Russia was supplying command-and-control units, artillery spotting and support, and other materiel to the separatists.
"Folks have taken their eye off of Ukraine a little bit because of what's happening in Syria," Breedlove said.
"It's technique they've employed in the past, a couple of times. Invade Crimea. Take the world's eyes off of Crimea by invading Donbass. Take the world's eyes off of Donbass by getting involved in Syria."
"This is part of a larger construct by Russia and we need to be thinking holistically about our response," he said.
"We need to remember that these are connected."
The conflict between Ukrainian forces and Russia-backed separatists who hold parts of the Donetsk and Luhansk regions, has killed more than 8,000 people since April 2014.
The Russian missile tests, which appeared to be the largest it has conducted in at least a year, included the launch of a Kalibr cruise missile from a Russian ship in the Caspian Sea, as well as intercontinental ballistic missiles from a nuclear submarine in the Barents Sea in the north and one in the Sea of Okhotsk, off Russia's eastern coast, the Defense Ministry said.
The exercises also included the firing of a land-based Topol missile from Plesetsk in northwestern Russia, Tu-160s strategic bombers launching cruise missiles in the northern Komi region and the Pacific peninsula of Kamchatka, and an Iskander cruise missile fired at Kapustin Yar in southern Russia.
The tests, and Breedlove's comments, come as rhetoric between Moscow and the West continues to ratchet up, with U.S. and NATO aircraft flying in sometimes close proximity to one another in Syrian airspace.
They also come as NATO stages its largest training exercises in more than a decade, with 36,000 troops from 30 countries participating in the drills off of Spain and Portugal.
NATO officials said the Trident Juncture drills had been planned for months, but also highlighted the alliance's concerns with Russia's often bellicose actions in Eastern Europe and elsewhere.
The Russian military campaign in Syria, which began on September 30 after weeks of a stealth build-up of troops and equipment, is its largest outside the former Soviet Union in decades.
With advanced military weaponry such as Su-30M fighter jets and the Kalibr cruise missiles being used in the air campaign, many analysts believe the Syria operation is aimed at sending a message that Russian military capabilities have returned in full.
Earlier this week, two strategic Tu-160 bombers flew within 2 kilometers, and at a height of 150 meters, to the U.S. aircraft carrier Ronald Reagan in the Pacific Ocean off East Asia, prompting officials to scramble F/A-18 fighter jets to escort the bombers.
Asked why he thought the Kremlin had deployed to Syria, where the regime of President Bashar al-Assad is a close ally, Breedlove said, "Putin wants to be seen as equal on the world stage, as a world power."
"Putin needs eastern Mediterranean ports and airfields. Putin sees the Assad regime as a guarantor of those ports. Putin wants the world's eyes off of Ukraine, to put the focus on Syria, then normalize Donbass. I think he wants to take the world's eyes off of Ukraine," he said.
Source: Radio Free Europe