WASHINGTON—Ukraine's interim government has appealed for U.S. military aid, including arms, ammunition and intelligence support, according to senior U.S. officials. But the Obama administration has agreed to send only military rations for now, wary of inflaming tensions with Russia.

The U.S. decision reflects the Pentagon's reluctance to be seen as directly supporting Ukraine's beleaguered armed forces during the standoff with Russia, which has seized the Ukrainian region of Crimea.

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