YOKOTA AIR BASE, Japan — U.S. Defense Secretary Leon Panetta today lashed out at North Korea for “reckless and provocative” acts and criticized China for a secretive expansion of its military power.

Panetta, who arrived at this U.S. air base on the second leg of a weeklong Asia tour, spoke out about North Korea and China in an opinion piece published today by Japan’s Yomiuri newspaper before his arrival.

He wrote that Washington and Tokyo share common challenges in the Asia-Pacific. “These include North Korea, which continues to engage in reckless and provocative behavior and is developing nuclear weapons and ballistic missiles, which pose a threat not just to Japan but to the entire region,” he wrote.

If any changes are made to U.S. forces in the Pacific, he said, it would be to “strengthen” their presence.

“We are not anticipating any cutbacks in this region,” he told several dozen U.S. and Japanese troops standing in front of huge side-by-side American and Japanese flags. “If anything, we’re going to strengthen our presence in the Pacific — and we will.”