U.S. Defense Secretary Chuck Hagel said permanently stationing an additional U.S. Army brigade in Europe is among options to beef up security as Russian troops remain massed along Ukraine's eastern border.

The North Atlantic Treaty Organization (NATO) has asked its top military commander, U.S. Air Force General Philip Breedlove, to study "a number of new possibilities, new measures, new options that we and NATO should consider," Hagel said in an interview yesterday in Honolulu with Bloomberg News and Bloomberg Television.

Asked if those included permanently stationing a third brigade of 5,000 troops in Europe, Hagel said, "That's all part of the measures that could be considered."

Reports of Russia withdrawing some of its forces from the Ukrainian border are unconfirmed, he also said.

"There are troops that are moving around, we know that, but no indications of any significant movements of those large troop deployments along the border, away from the border," he said.

As part of a U.S. defense strategy approved in 2012 by President Barack Obama, the Pentagon withdrew from Europe two of its four Army brigades, including 10,000 troops and their equipment, and eliminated them. The strategy assumed Europe would remain peaceful and Russia would be a partner rather than an antagonist, laying the foundation for the administration to turn more of its attention to Asia.

The options being considered by Breedlove, including sending a U.S. warship to the Black Sea, aren't intended as offensive moves, Hagel said in Hawaii, where he's hosting a meeting of defense ministers from southeast Asian nations.

"NATO is a defensive organization," he said. "It's not an offensive or an invasion institution."

The alternatives being studied are intended to ensure "that we have the adequate defenses to protect those 28 nations that we are all obligated to protect each other. So no, there's no escalation on our part."

The administration's defense strategy isn't being re-examined based on Russia's aggressive actions in recent weeks, Hagel said.

"I don't think you can develop strategic interests based on one episode or two episodes," he said. "No, we don't have to go back and relook at the strategy."

Still, he said Russia's invasion of Crimea, which it has now annexed, has raised the risk that the Pentagon may not be able to meet all its obligations unless Congress increases defense spending.

Added Risk

"If we don't get the resources that we've asked for -- and we've laid all this out -- then there'll be increased risk," Hagel said. "Any time you've action by a nation like Russia that took control and violated the territorial integrity of a nation, sure that's an additional risk."

The annexation of Crimea didn't stem from a poor understanding of Russia's president by Obama, Hagel said. Some Republicans lawmakers have portrayed Obama as naive about his counterpart in Moscow.

"I don't think anybody misjudged Vladimir Putin," Hagel said. "Let's go back to 2008 when President Putin invaded Georgia. So this isn't a particularly new approach that he's taking."

Hagel said the U.S. isn't "retreating from any part of the world," with "400,000 men and women stationed all over the world in a hundred countries."

He also stood by the administration's pledge to rebalance defense policy toward Asia, with the meeting he is hosting in Honolulu as a symbol of that commitment.

"We've tremendously important interests, security, economic, diplomatic interests in this area," Hagel said.

Hagel leaves Honolulu today to visit Japan, China and Mongolia.