Sen. Dan Sullivan (R., Alaska) warned that the United States is lagging behind in the Arctic amid Russia's push to increase its military presence in the region through a rapid buildup of ice-capable ships and infrastructure.

Sullivan, a member of the Senate Armed Services Committee, cited an unclassified strategic report recently released by the Department of Defense to Congress that offers a vague prescription for countering Russian expansion in the region. He said while the Pentagon's renewed attention to the Arctic is encouraging, the United States still has a "long way to go" to catch up.

"We're late to the game," Sullivan told the Washington Free Beacon.

"Russia has been changing the facts on the ground in a very major way that is somewhat analogous to what's going on in the South China Sea, where we start to talk about it, but in the meantime others are acting and all the sudden we find ourselves behind strategically," he said.

Russia's has recently built 14 airfields and arctic ports, four new Arctic brigade combat teams, and 40 icebreakers, some of which are nuclear powered, with another 11 in development. The Unites States has one functioning icebreaker—the other is broken, Sullivan said.

Russian President Vladimir Putin also is moving to re-open shuttered Soviet military, air, and radar bases on remote Arctic islands, marking the biggest military push by the Kremlin in the region since the Cold War.

Sullivan last year worked alongside Sen. Angus King (I., Maine) to pass an amendment to the annual National Defense Authorization Act requiring the Defense Department to update its Arctic military strategy.

In its new report, the Pentagon cited "friction points" arising from Moscow's claim to three international waterways that run along a critical shipping passage off of Russia's Arctic coast.

Russia requires permits for any ships navigating along the Northern Sea Route despite the U.S. objection that the rule violates international law. The Pentagon predicted tensions would escalate as rising temperatures continue to melt Arctic sea ice, opening up shipping lanes and access to natural resources.

Diminishing sea ice threatens to open a waterway directly to North America from Russia while damaging U.S. infrastructure along the coast, including detection and warning capabilities the Defense Department uses to track incoming ships.

Though the Pentagon strategy urged Congress to approve additional funding for the department to modernize infrastructure, expand its naval fleet, and enhance training and exercises in the region, Sullivan said it does not go far enough.

The Trump administration has signaled it would prioritize developing a U.S. strategy in the Arctic.

Defense Secretary James Mattis testified during his confirmation hearings last month that the Arctic is a "key strategic terrain," and that it was "not to our advantage to leave any part of the world" to others.

"The fact that Gen. Mattis has indicated to me this is important is a good reboot of strategy in an important part of the world that needs the Pentagon's increased focus and attention," Sullivan said.