YOKOTA AIR FORCE BASE, Japan — Against the backdrop of Russia’s takeover of Ukraine’s Crimean region, Defense Secretary Chuck Hagel said Saturday that a key message he will deliver to leaders in Tokyo this weekend is that the U.S. is strongly committed to protecting Japan’s security.

Hagel said it is understandable for nations to be concerned as they watch the events unfold in Ukraine, where Russian troops are still massed along the border. The issue reverberates in Asia where China, Japan and other nations are locked in bitter territorial disputes, including over disputed islands in the East China Sea.

“It’s a pretty predictable, I think, reaction, not just of nations of this area and this region but all over the world,” Hagel told reporters traveling with him to Tokyo. “I think anytime you have a nation — Russia in this case — try to impose its will to refine and define international boundaries and violate the territorial integrity and sovereignty of a nation by force, all of the world takes note of that.”

Assistant Secretary of State Daniel Russel also said this week that Russia’s annexation of Crimea heightened concern, particularly among some Southeast Asian nations, about the possibility of China “threatening force or other forms of coercion to advance their territorial interests.”