Leading article: Russia and the art of nuclear diplomacy

Experience has taught that extreme caution is in order when reporting any breakthrough in the labyrinthine diplomacy concerning Iran and its nuclear programme. And the agreement, reached in principle between Russia and Iran, that would result in Iran having its uranium enriched in Russia is at a very early stage.

With all the necessary caveats, however, yesterday's announcement constitutes progress. For weeks now, international efforts to persuade Iran to suspend its nuclear programme had seemed vain and even counter-productive. The more directly the Europeans and the United States told Iran that its decision to restart its nuclear research programme was unacceptable, the more determined Tehran seemed to be to proceed. Even the line that Iran had initially drawn between its intention to engage in research only for nuclear energy, not a nuclear bomb, seemed to become frighteningly blurred.

For all its apparent refusal to compromise, however, Iran never broke off talks completely. And while Russia might seem a questionable partner for the West in this venture, Moscow has long understood the danger that a nuclear Iran would present, not least to its own southern flank. It supported the European diplomatic effort early on.

The difficulty was to persuade Iran to make that concession. At least two obstacles stood in the way: Tehran's right as a signatory to the Nuclear Non-Proliferation Treaty to conduct nuclear research for peaceful purposes and the sense of Iranian national pride into which the Prime Minister, Mahmoud Ahmedinejad, had successfully tapped during his election campaign. It is unrealistic to expect that these factors will not complicate implementation of an agreement, even if it is confirmed.

It is, however, in everyone's interests to make this agreement stick. Iran might have sacrificed some pride, but it will be saved from becoming an international pariah and, possibly, from a military strike. The Europeans will have their confidence in a diplomatic solution vindicated, while the United States will be able to claim that the greatest risks from Iran's nuclear programme have been averted.

Russia, perhaps, has most at stake. Not only does it have an economic interest in nuclear cooperation with Iran, it also wants to win its spurs as an international player. Moscow's overture to Hamas after its Palestinian election victory can be seen in the same light.

The priority now is for all concerned to proceed discreetly. The last thing anyone should do is to crow about concessions Iran may or may not have made. The art of diplomacy requires that everyone remain diplomatic for the duration.