Hagel moves to reassure Japan on security ties

US Defense Secretary Chuck Hagel sought on Saturday to reassure Tokyo that the United States is committed to Japan's security, as Russia's annexation of Crimea raises eyebrows in a region facing its own territorial disputes.

The United States and its allies have made clear they have no military plans to defend Ukraine, which is not a NATO member, but instead are moving to diplomatically isolate Russia and impose limited sanctions.

Critics in the West say such moves are too weak to return Crimea to Ukrainian control.

Although his trip was planned long before the events in Crimea, Hagel said "another reason I'm here is to reassure our allies of our commitments to their security".

He said defense ties between the US and Tokyo had strengthened in recent years with the deployment of advanced surveillance aircraft in Japan and plans to station a second early-warning radar system there later this year.

Hagel defended the US strategy to punish Russia and told reporters ahead of two days of talks with Japanese leaders that it was natural that "allies are going to look at each other to be assured", given the crisis in Ukraine.

"It's a pretty predictable, I think, reaction not just of nations of this area, of this region, but all over the world. It has to concern nations," he said.

But Hagel rejected any suggestion of weakness as he emphasized US commitments to Japan.

Washington has said it takes no position on the sovereignty of China's Diaoyu Islands, which Japan claims as its own. However, it recognizes them as being administered by Japan and says they fall under the US-Japan Security Treaty, which obligates the US to come to Japan's defense.

Addressing US and Japanese forces at Yokota Air Base on Saturday, Hagel said one of the goals of his trip to the region was to assure allies that the US is committed to "our treaty obligations".

"We're serious about that," he said.

In recent months, Japanese Prime Minister Shinzo Abe's drive to beef up Japan's forces while loosening constitutional limits on military actions overseas has been gaining momentum.

Last week, his government unveiled an overhaul of a decades-old ban on weapons exports.

In an interview published before his arrival, Hagel said he welcomed the possibility of Japan giving its military a greater role by allowing it to come to the aid of allies under attack.

"We welcome Japan's efforts to play a more proactive role in the alliance, including by re-examining the interpretation of its Constitution relating to the right of collective self-defense," Hagel said in a written response to the Nikkei, Japan's main financial newspaper.

Reuters-AFP