There are two ways of looking at the efforts of Turkey and Brazil to resolve the dispute about Iran's nuclear programme. One dismisses the initiative as collusion with Tehran's attempt to derail a fourth round of United Nations sanctions; another welcomes a recognition in Ankara and Brasilia that rising powers have a stake in sustaining a rules-based global order.

Unsurprisingly, the default response in the west has been the former. Reactions in Washington, London and elsewhere to the agreement brokered by Turkey's Recep Tayyip Erdogan and Brazil's Luiz Inácio Lula da Silva ranged along a spectrum from condescension to intense irritation. Ankara and Brasilia, at best, were dupes.

The bargain struck by the two leaders with Iran's Mahmoud Ahmadi-Nejad, if implemented, would see Iran transfer to Turkish custody a large proportion of its stockpile of enriched uranium. In return, Tehran would be supplied with the more highly-enriched material used in medical isotopes. The risk of an Iranian bomb would be reduced, while Tehran would retain what it sees as a sovereign right to mastery of the nuclear fuel cycle.

There is nothing novel about the idea. It is modelled on an offer made last autumn by the five permanent members of the UN Security Council. The difference is that this first proposal envisaged the Iranian uranium would be sent to Russia.

The latest plan raises plenty of legitimate questions. Among other things it does not tell us what Iran proposes to do with the rest of its uranium stockpile and why it is continuing to produce more. Tehran has also yet to explain why it is now enriching to a higher concentration.

The timing of the deal raises the justified suspicion that Iran's primary objective is to upset the US-led move towards further UN sanctions. During many years of negotiations with the west, Tehran has hardly been subtle in its tactics: the pattern has been one of apparent concessions at moments of pressure followed by lengthy prevarication and enrichment as usual. On a generous interpretation, one western diplomat told me, Mr Erdogan and Mr Lula da Silva were naive.

Against this background, the US, France and Britain have unveiled their plans for the latest sanctions – this time directed at Iran's Revolutionary Guard – with obvious satisfaction. Turkey and Brazil might think their deal had abrogated the need for further punitive measures, but China and Russia had been persuaded otherwise.

Perhaps I am overly cynical but I detect a certain petulance here. Turkey and Brazil have temporary seats on the Security Council, and it is as if the permanent members are affronted the two nations should presume to strike out on their own.

The Iranian nuclear issue, you could almost hear diplomats saying, is an argument that has to be settled by the established powers. If others want to help that is fine – but they should do so by backing the west's plan rather than coming up with crackpot ideas of their own.

There are several reasons why this is short-sighted. Most obviously the permanent five have got just about nowhere so far. Even those arguing that sanctions are the only way to coerce Iran into toeing the UN line do not really believe the measures can work on their own. If Tehran really has decided to build the bomb, a squeeze on the Revolutionary Guard will not change its mind.

It is evident, too, that in the event that the present regime were to change course and seek an accommodation on its nuclear programme, ways would have to be found to ensure it was not seen as capitulating to the great, and lesser, Satans of the west. A deal struck with a neighbouring Islamic state might – and I emphasise the might – be a route out of the impasse.

For Mr Erdogan's government the attempt to broker a deal is a natural extension of Ankara's active regional diplomacy. The last few years have seen a marked rise in both Turkey's economic prosperity and its political confidence. As France, Germany and others have found reasons to exclude it from the European Union, Turkey has turned eastwards.

Ankara's rising stature in the region has been based on the brilliantly simple proposition that nations that want to project influence should start by fixing their own disputes. Mr Erdogan has settled long-running arguments with Syria and Iraq and sought to lower tensions in the Caucasus.

The neighbourhood problem-solving has not been universally successful but it has been sufficiently so to turn Turkey into a big regional player. Mr Erdogan's government now shows the political confidence that comes with understanding that it has opened up options for itself beyond frustrating and fruitless negotiations in Brussels about the terms under which it might at some point qualify as a "European" power. Here, I think, lies a source of the irritation in Washington and elsewhere about the latest initiative.

The off-stated ambition of western governments is that the world's rising powers should bear some of the burden of safeguarding international security and prosperity. The likes of China, India and, dare one say, Turkey and Brazil, are beneficiaries of a rules-based global order and, as such, should be prepared to contribute. They should, in a phrase coined some years ago by Robert Zoellick, act as stakeholders in the system.

Seen from Ankara or Brasilia, or indeed from Beijing or New Delhi, there is an important snag in this argument. They are not being invited to craft a new international order but rather to abide by the old (western) rules. As I heard one Chinese scholar remark this week, it is as if the rising nations have been offered seats at a roulette table only on the strict understanding that the west retains ownership of the casino.

As it happens, the US understands better than Europeans the shifting distribution of power. Barack Obama's administration has been thinking hard about the new geopolitical geometry, even as Europe remains trapped in its anxiety to cling on to the old Euro-atlantic order.

In its excellent exercise in crystal-ball gazing, Global Trends 2025, the US National Intelligence Council presciently included a scenario in which Brazil acts as a mediator at a moment of crisis in the Middle East. Imagining a different future, though, is not the same as coming to terms with it. If the west wants global order, it has to get used to others having a say in making the rules.