LONDON -- While the world has been busy fighting wars and making peace, could the United Kingdom's atomic stockpile have quietly become an anachronism?

Government officials and issue experts here are hotly debating that very question, what with the Cold War long over, the two global superpowers shrinking their nuclear arsenals and Washington looking to reduce the role of these most-deadly weapons in its own security posture.

“Having looked at all the different threats, it’s very difficult to come up with a likely threat for which a nuclear deterrent would be relevant,” says Paul Ingram, executive director of the British American Security Information Council.

One frequently cited example of a possible future threat to Britain is Iran. But Ingram and a number of other security pundits wonder whether it is realistic to think that the Persian Gulf nation -- if it ever obtained nuclear arms -- would select Great Britain as its target.

“These days, we do not [loom] large in the calculations of Iran’s military balance,” Peter Jenkins, a former U.K. ambassador to the U.N. nuclear watchdog agency in Vienna, said at a Sept. 23 British Pugwash discussion. “Unless grievously provoked, they would not dream of wasting precious nuclear weapons on us.”

Others, though, insist that now is not the time for Britain to denuclearize -- or to even make a significant move in that direction.

Much of the British concern about shedding their own arsenal has to do with the United States, the United Kingdom’s closest ally. Washington’s focus is no longer as firmly placed on its allies across the Atlantic as it used to be. To some, that suggests that the U.S. nuclear umbrella over the United Kingdom and the rest of NATO may not be quite as protective as it once was.

In fact, U.S. attention increasingly is consumed by an array of domestic issues -- from the economy and federal spending to guns and privacy rights -- and the Asia-Pacific region is frequently elbowing out other interests in Washington’s trimmed-back agenda abroad.

So despite President Obama’s long-term “Prague vision” of ridding the world of nuclear weapons, the reality of today’s Washington appears to be having an unintended collateral effect: Driving the British government to cling ever more tightly to its own nuclear arms.

There are some mitigating factors. Few, if any, serious thinkers in either capital anticipate a time when another country will take London’s place as Washington’s most trusted ally. Many say the United States can indeed be counted on into perpetuity to defend its premier transatlantic partner from any existential threats, even if it means lobbing nuclear weapons on London's behalf.

“I cannot conceive of the United States not being there to provide us with a nuclear umbrella,” Jenkins said.

What's more, Britain's atomic arsenal is not very large compared to that of the United States or Russia, and is getting yet smaller over time.

In the coming years, the United Kingdom is expected to continue gradual unilateral reductions of its estimated current stockpile of 225 warheads. The nation likely will have no more than 180 such weapons by the mid-2020s, the London Guardian reported in August.

But there is more talk here lately of the possibility that U.K. and U.S. interests around the globe will increasingly diverge in coming decades. Might there come a day when Washington won’t necessarily, in every instance, have London’s back?

“In the end … there’s no rationale for having a U.K. nuclear force unless there are circumstances in which a potential adversary might believe that the United States won’t use nuclear weapons in a scenario in which the U.K. would,” said Malcolm Chalmers, director of U.K. defense policy studies at the Royal United Services Institute.

Though British leaders are largely reluctant to voice that question publicly, many seem keen to retain some extra measure of military and diplomatic clout for those times when Washington's attention is fixed elsewhere, according to a U.K. lawmakers and security analysts of various political stripes.

The U.K. governing coalition partners agree that the nation's nuclear deterrent force should be maintained into the foreseeable future, though there is discord over appropriate levels of readiness and cost.

The government recently released an unclassified version of a three-year study on potential alternatives to its $30 billion “like-for-like” strategy of replacing by 2040 today’s four Vanguard-class ballistic-missile submarines with an equivalent number of modern Successor-class vessels.

Demanded by Liberal Democrats as a condition of joining a governing coalition with the Conservative Party in 2010, the analysis found only one cheaper option that could be “credibly” considered: reducing to just three replacement submarines for a lifecycle savings of roughly $3 billion.

This alternative, though, would demand jettisoning the U.K. policy of keeping at least one submarine at sea at all times -- what Brits call their “continuous at-sea deterrent.” Liberal Democrats are eager to embrace a relaxation of the CASD approach as a useful “step down the nuclear ladder,” but their Tory governing partners firmly reject the idea.

U.K. Defense Secretary Philip Hammond called the Liberal Democrat proposal "reckless" in a July commentary published in the Daily Mail.

"The number of nuclear weapons in the world remains at well over 17,000. Russia is spending $150 billion upgrading its forces. And there are states, such as Iran, which already have ballistic missiles and are seeking to acquire nuclear weapons," Hammond wrote. "How can anyone be confident that the global security environment will not change in the next 10 years? This is not the time to let down our guard."

A final decision on the matter is expected in 2016, after the nation’s next elections.

In the run-up to that potentially momentous verdict, politicians debate and defense experts ponder.

“I believe the Trident is the U.K.’s last unreformed bastion of Cold War thinking,” Member of Parliament Danny Alexander -- the Liberal Democrat chief secretary of the Treasury who led the government’s Trident review -- said at a Sept. 11 event in Washington. He does not favor disarming but does advocate modestly reducing the Trident-armed submarines' operational readiness to launch weapons.

“A different approach would, I believe, allow the U.K. to contribute meaningfully to the new multilateral drive for disarmament initiated by President Obama, while maintaining our national security and our ultimate insurance policy against future threats,” Alexander said.

“Do you think other countries care enough about what Britain does [with its nuclear deterrent]?” mused Ian Wallace, a former Defense Ministry senior official, speaking at the same Brookings Institution event.

For some, London's desire to retain nuclear arms is all about the United Kingdom maintaining close access to a global superpower, even if Washington is by most accounts a hegemon in gradual decline.

Some of those who favor keeping the U.K. nuclear deterrent see the arms as “a way of cementing that nuclear relationship with the U.S., so we have a closeness of consultation on every aspect of nuclear policy," Chalmers said. "If we weren’t in the [nuclear] business, we wouldn’t be consulted."

According to Ingram, U.K. nuclear arms have become little more than a pretext for London to ride on Washington’s coattails, now that the glory days of the British Empire have been left behind -- almost akin to a dysfunctional marriage.

With the United States at times choosing to go its own way, “the British start to wonder about being cut out of the special relationship,” he told Global Security Newswire. “The corresponding fear is that if Britain were to get rid of its nuclear weapons, that symbol of the relationship will die, and the Americans will walk away.

“It is this very sense of insecurity and inferiority, this fear, that is at the heart of the co-dependent relationship, [and] that keeps the British in line,” he said.

Some Brits would call that poppycock. They say there could be real threats on the horizon that justify continued retention of the weapons. For one thing, China could become a dominant threat around the globe in the decades to come, and U.K. nuclear arms could help offset this rising power, according to this line of thinking.

But the potential resurgence of Russia as a major threat to Europe in the long term is actually reason enough for the United Kingdom to hang onto its deterrent force, many British thinkers are saying.

“Whatever decision we take has got to be for 40 to 50 years,” said Sir Malcolm Rifkind, a Conservative member of Parliament who has served as defense secretary and foreign secretary, among other top posts over a long career in public service.

Moscow is “the only possible aggressor with nuclear weapons in the short- to medium-term,” he said in an interview late last month at his Portcullis House office. “Historically Russia has always felt it could only guarantee its own security by controlling the territory around it.”

So why abandon a powerful deterrent that you’ve already got? Rifkind asked.

“It’s so much easier just to object to the principle: ‘These are wicked, horrible things and we don’t want anything to do with them,’” Sir Lawrence Freedman, a professor of war studies at King’s College London, said in an interview. “The issue is whether you want to be a nuclear power. I think it’s a genuinely difficult position for a country like Britain to have a radical departure on, because as things stand, it’s not obvious as to why you would.”

Rather, according to some issue experts, the continued interest in preserving a small and ready U.K. atomic arsenal translates into something more nuanced: Continued confidence in London about influencing events on the world stage -- unilaterally, if need be.

Imagine, for example, a future scenario in which a nuclear-armed Iran sponsors militants bent on disrupting the oil fields of one of its Persian Gulf neighbors -- oil on which the United Kingdom continues to depend, even as the United States has become more energy independent.

“If we get drawn into a conflict, how is our confidence in responding affected by [Iran’s nuclear arsenal]? How is Iran’s calculus affected, depending on whether or not possession of nuclear weapons is unilateral -- only on Iran’s part -- or mutual?” asked Shashank Joshi, a research fellow at the Royal United Services Institute, also speaking at the Pugwash event. “I think it may affect judgments at the margin, and it may weigh upon the minds of decision-makers.”