Barack Obama has just spilled the exact number of nuclear weapons the United States deploys around the world – for decades a closely guarded secret.

Russian security analysts say they're impressed with President Obama's disclosure, which puts pressure on Moscow to reciprocate. But don't hold your breath waiting for a Russian response. Because Moscow relies much more heavily on its nuclear arsenal for security and regional influence than the US does, a dramatic announcement is unlikely, analysts in Russia say.

"It's a big PR victory for Obama, and a very strong signal that his talk of a nuclear-weapons-free world is not just empty rhetoric," says Alexander Konovalov, president of the independent Institute for Strategic Assessments in Moscow. "But for Russia it's not so easy to match this step, due to differences in our security doctrine and the role of nuclear weapons in our defenses."

FAS calls on Russia to reciprocate

Ahead of the opening of the Non-Proliferation Treaty (NPT) Review Conference in New York, the Obama administration revealed a US nuclear stockpile of 5,113 nuclear warheads as of September 2009. That includes all active weapons, both strategic and tactical, but not "several thousand" more that are awaiting dismantlement under arms control accords.

The Federation of American Scientists, which has been producing the best estimates of global nuclear arsenals from public sources for the past 30 years, noted proudly in a statement Tuesday that the Pentagon's official count is just 13 bombs off its own latest guess, and added that the US move "ends years of unnecessary and counterproductive secrecy" about atomic arms.

"Disclosing the size of the US nuclear weapons stockpile puts pressure on other nuclear-weapon states to reciprocate," the group says. "Russia, whose arsenal is more difficult to track and assess, should respond by divulging comparable information about the size and status of its nuclear stockpile."

The organization estimates that Russia currently deploys around 2,600 strategic nuclear warheads and 2,050 tactical ones. The exact number of strategic weapons – those with intercontinental capability, based missiles, submarines or bombers – would have been provided to the US in the course of negotiations for the recently signed START accord.

"Tactical" nuclear warheads usually have a smaller explosive yield than "strategic" ones and are typically mounted on missiles with a range of about 300 miles or less.

New Russian doctrine lowers threshold for using nukes

Russian analysts insist that the numbers of tactical weapons in Moscow's arsenal will not be so easy to estimate, or to divulge.

The US is moving toward a nuclear-weapons-free world because it believes there are no military objectives the US armed forces couldn't achieve by using conventional arms alone, they argue.

By contrast, Russia, whose conventional forces are at their weakest point in decades, has grown far more dependent on nuclear weapons for its security. The latest Kremlin security doctrine actually lowers the threshold for using nuclear arms even in a small local conflict.

"There is not the slightest possibility that Russia will reveal the number of tactical nuclear weapons it holds," says Vitaly Shlykov, a former deputy defense minister who now works as a civilian adviser to Russia's Defense Ministry.

"The main thing that justifies Russia's claim to be a major regional power is its nuclear arsenal, and there is considerable leeway in our nuclear doctrine to use tactical nuclear weapons in an emergency," he says. "The mystique surrounding these weapons – that is, their numbers and the conditions under which Russia might employ them – is considered a very important advantage. I don't believe Russian leaders would contemplate giving this up."

Debate about whether Russia should respond in kind

Gennady Chufrin, an arms control expert with the government's Institute of World Economy and International Relations, says that all Russian nuclear weapons are based on Russian soil, while the US still deploys tactical nuclear weapons in Europe, Korea, and elsewhere.

"Russia would be very interested in negotiating a treaty covering tactical nuclear weapons, so why would we reveal the figures in advance?" he asks.

But others argue that Russian leaders will find it difficult to maintain a posture of cold-war-style secrecy after Obama's sweeping disclosure of US capabilities.

"If we don't respond, it'll hurt Russia's image," says Yevgeny Bazhanov, vice rector of the official Diplomatic Academy in Moscow, which trains Russian diplomats.

"If Obama was strong enough to overcome the resistance of his military establishment and take this dramatic step, our leaders cannot do otherwise," he says. "It's a matter of honor for them."

Related:

NPT 101:

Part 1: How relevant is the cold war treaty in an age of terrorism?

Part 2: Which countries have nuclear weapons?

Part 3: Why Iran sees nuclear 'hypocrisy

Part 4: Clash between nuclear haves and have-nots

Part 5: Is Iran violating the nuclear treaty?