There is no country on Earth more committed to global nuclear disarmament than Japan. Ever since experiencing firsthand the horrors of nuclear weapons at Hiroshima and Nagasaki, the Japanese government and people have been steadfast in calling for the total elimination of nuclear weapons from the planet.

Japanese were among the first and loudest to applaud a few years back when a group of senior American statesmen — former Secretaries of State Henry Kissinger and George Schultz, former Defense Secretary William Perry, and former Sen. Sam Nunn — called for the United States to start honoring its nuclear disarmament commitment under the Nuclear Non-Proliferation Treaty. These are not tree-hugging idealists. All are hard-nosed realists who argued that America was safer in a world without nuclear weapons and that it was important that the United States be seen as leading the world in this direction, rather than merely playing lip service to such calls.

President Obama agreed with this logic. He spoke often during his campaign about the need to eliminate nuclear weapons. He now appears ready to take a major step in this direction with the agreement to begin talks with Moscow "on the terms and time frame" for a follow-on to the Strategic Arms Reduction Treaty.

One would expect, therefore, that the Japanese would be delighted. Not so fast. True, many Japanese are still eager to see deeper, even drastic, cuts in the world's two largest nuclear inventories. But others are concerned that rumored cuts — some are proposing both sides reduce their respective arsenals to 1,000 or fewer nuclear weapons — would be "too much, too soon." They are quick to remind President Obama about the other half of his "dual commitment," namely that the U.S. would not unilaterally disarm and would maintain a strong nuclear deterrent until such time as all weapons could be verifiably eliminated.

Herein lies the core of their concern. If only the U.S. and Russia had nuclear weapons, deeper cuts in both arsenals would make a lot of strategic sense. But the NPT recognizes five nuclear weapons states — the U.S., Russia, China, France and Great Britain — and while most Japanese don't lose a lot of sleep over French or British nuclear weapons, they do worry constantly about China's growing nuclear weapons capability and the impact that deep reductions in the U.S. arsenal would have on America's "extended deterrence."

Then there's North Korea, which along with India and Pakistan are self-declared and demonstrated nuclear weapons states. The breakdown in six-party talks has demonstrated how difficult it is to verify even the smallest nuclear holdings — Pyongyang is suspected, at worst, of having six to eight weapons worth of plutonium. Nonetheless, and despite the concerns of many Japanese to the contrary, America's overwhelming nuclear and conventional force superiority renders the North Korean threat manageable. But can the same be said for China, especially if it continues to increase its nuclear arsenal in the face of reductions by the other four nuclear weapons states?

Today, China follows a "minimum deterrence" strategy. It claims no interest in expanding its arsenal to the levels currently held by the Russians or the U.S.; it just wants a force sufficient to deter the U.S. from using such weapons against China. Presumably then, significant reductions in U.S. and Russian inventories could be met with similar reductions in Chinese nuclear holdings. Perhaps, but Beijing's position so far on nuclear arms reduction efforts is "call us when you get down to our numbers and then we can talk." China has not officially announced what those numbers are, but intelligence estimates put Beijing's holdings at around 300 to 400 weapons.

At a recent Pacific Forum U.S.-Japan strategic dialogue, virtually every Japanese security specialist (and most Americans in the room) argued that a drastic reduction in the U.S. nuclear arsenal could tempt Beijing to start growing its nuclear arsenal in an attempt to achieve nuclear parity. This could have a chilling effect on America's extended deterrence capability, they warned, and cause Tokyo to question the reliability of the American nuclear umbrella.

President Obama needs to take heed of these warnings. The time has come for Washington and Moscow, as they begin deliberations on further significant nuclear arms reductions, to insist that China and the others join the dialogue and place their own nuclear arsenals on the table. While it would be unrealistic to expect one-for-one reductions from those with smaller inventories, all should agree to equivalent percentage-based cuts; a 20 or 50 percent cut in Russian and U.S. arsenals should generate a similar cut in Chinese, French and British forces.

This, of course, will compel Beijing to finally become more transparent as to the extent of its nuclear weapons holdings and future force development plans, but moving down the road toward genuine reductions and eventual elimination of nuclear weapons requires all the nuclear weapons powers, led by the five recognized nuclear weapons states, to move in unison, if real progress is ever to be made.

Ralph Cossa is president of the Pacific Forum Center for Strategic and International Studies, a Honolulu-based think tank specializing in current and emerging political, security, economic and business issues across the Pacific Rim. He wrote this commentary for The Advertiser.