Both the critics and the supporters in the United States of President Barack Obama's nuclear agreement with Iran are right.
The critics are correct that the agreement to limit Teheran's nuclear programme is, from a US point of view, a deeply disappointing outcome.
The deal does impose real limits on Iran's nuclear programme, but not for long.
It only defers, for little more than a decade at best, the day when Iran can build nuclear weapons, and it does nothing to strengthen US leadership against the challenge posed by Iran's growing power and influence across the Middle East.
But the nuclear agreement's supporters are also right.
This is the best deal available, and the only alternative to taking it, with all its faults, is to walk away from any deal at all.
We now live with the new reality that Iran is and will remain, at best, on or close to the threshold of being a nuclear power. That must affect the strategic and broader geopolitical calculations of everyone in the Middle East.
And that means living with a nuclear-armed Iran sooner rather than later.
That suggests it is better to do the deal than abandon it, even though it does so much less than what Washington was aiming for when it began this process almost 10 years ago. Back then, the idea was to crush Iran's nuclear ambitions and contain its growing regional influence once and for all.
Americans must now be asking themselves why that goal is being abandoned so they now face so stark a choice between two such bad alternatives.
How come there are no better options available to the world's most powerful country, they wonder, when the stakes are so high? Iran is, after all, the original "rogue state", defying US power and prestige in the most blatant, and at times humiliating ,ways for over 35 years.
Moreover, preventing such states from getting nuclear weapons has arguably been the US' No. 1 foreign-policy priority since the Berlin Wall came down in 1989.
So leaving Iran, of all countries, with a path to nuclear weapons sometime in the future seems like a particularly bitter failure.
Above all, it is an outcome which brings Americans face to face with the limits to their country's power.
The US is, and will always remain, an exceptionally strong country, but it is simply not as strong as Americans have been led to believe. Ever since the Soviet Union imploded, they have been told that the US stands unchallengeable at the apex of the global order, strong enough to shape the world to its wishes and in its image.
Of course, this confidence has taken a few knocks, for example, when the invasion of Iraq turned to ashes a decade ago.
The knocks have come harder and faster in the last couple of years, especially in Syria and Ukraine when crises have found the US struggling to frame an effective response. But the fact that it seems to have no choice but to accept Iran as a threshold nuclear power and a growing regional rival seems to be the plainest sign yet that the US is not as strong as everyone assumed.
The objectives it set itself a decade ago were simply unrealistic.
LIMITS TO U.S. POWER
Most obviously, the deal with Iran shows the limits of US military power. For years, US leaders have been blithely assuring everyone that if Iran did not abandon its nuclear programme, the US would destroy it by armed force.
But there has never been a viable military option to do more than disrupt and delay Iran's path to the bomb. It is simply too easy for Iran to conceal and protect the vital elements of the programme from US or Israeli air strikes, no matter how well planned or precisely executed. The military option was never more than big talk, whether those who talked big about it knew this or not.
More broadly, however, it shows the limits of US diplomatic power, and that is not because the deal with Iran shows poor diplomacy on Washington's part.
On the contrary, it is something of a negotiating triumph.
Washington created and enforced the draconian economic sanctions which brought Iran to the table in the first place, held together a disparate negotiating team which included rivals China and Russia, and pushed the Iranians to make some big concessions. There is no reason to think that they have not got the very best deal with Iran that it was possible to get.
So the agreement now on the table shows US diplomacy at its best, but it also shows how little even the best diplomacy can deliver against a really determined adversary like Iran.
LIVING WITH REALITY
That being so, we now live with the new reality that Iran is and will remain, at best, on or close to the threshold of being a nuclear power.
That must affect the strategic and broader geopolitical calculations of everyone in the Middle East.
The country whose strategic circumstances are least affected is the one making the most noise.
Alone among Iran's Middle East neighbours, Israel has the capacity to deter any Iranian nuclear attack with a highly credible threat of massive retaliation from its own formidable nuclear arsenal.
For all their wild talk, Iran's leaders would have to be literally insane to ever attack Israel with nuclear weapons.
The consequences are much graver for Iran's Arab neighbours like Saudi Arabia.
It is not just the prospect that their regional arch-rival will now be poised indefinitely within reach of nuclear capability.
The Iranian deal undermines their whole concept of regional security. For decades, they have relied both on the US' strength and on its loathing for Iran, to contain Teheran's ambitions for regional hegemony. Now they are also confronted by the limits of US power, and by Washington's evident hopes that the nuclear deal will pave the way for wider cooperation with Teheran on regional issues.
The more Mr Obama talks of recognising and working with Iran as a regional power, the more worried Iran's neighbours must become that their interests will be sacrificed as and when that happens. And who knows what steps they might take in response.
Along with the radical reshaping of Iraq and Syria, this will be another major factor driving the biggest transformation of the Middle East since 1918.
•The writer is a professor of strategic studies at the Australian National University in Canberra.
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