Until last week, it was not even clear where talks would happen.

On Friday, the five permanent members of the UN Security Council plus Germany (P5+1) will meet their Iranian counterparts in Istanbul, for a new round of negotiations over Iran's nuclear programme. There is no reason to be optimistic about the talks, despite the initial mood expressed by Brussels and Washington. Iran refused to rejoin talks for 14 months and played an elaborate game of brinkmanship over the location of the talks until the last minute - even suggesting Beijing, Baghdad and Damascus as possible venues for the meetings.

It has accepted that talks would occur without preconditions and its nuclear programme would be the focus of discussion - a sign that Western capitals read as proof that the combined pressure of economic sanctions and diplomatic isolation is working.

But Iran may not necessarily be willing to compromise. After all, Tehran is mostly defiant - words of moderation being expressed only by exiled figures like former nuclear negotiator Seyed Hossein Mousavian and his patron, former president, Akbar Hashemi Rafsanjani. Such articulations of a possible compromise voiced by Iranian opposition figures fall far short of the minimum required to build Western confidence after so much deception over the years by Iran.

There is also the possibility that Iran's nuclear programme may be advancing much faster than previously assumed by Western intelligence estimates. And there is the understandable temptation for Iran to accelerate its pace, in the light of three things: the growing threat of an Israeli strike; the mounting weight of economic sanctions; and the admonition, voiced by US President Barack Obama, that this round of negotiations may be Iran's last chance to avert pre-emptive military action. Iran may conclude that the regime would anyway succumb under the pressure of one of these three threats and would only survive if it pre-empted them by testing a nuclear weapon before an Israeli or American attack, or crippling sanctions were to undermine the regime beyond repair.

If so, then Iran may seek to use negotiations to buy time as it has done so many times before. This is the reason why the United States deployed a second aircraft carrier in the Persian Gulf only a few weeks after despatching additional minesweepers to the area.

Iran has pulled back from the brink before and its leaders may conclude that this time, too, they need to make concessions to ensure the regime's survival. But Western negotiators should not be too optimistic. Iran looks at the West and, politically, economically and militarily, it sees weakness all around.

This fact, combined with the constant stream of Western voices denouncing a possible military strike against Iran as a prospect worse than a nuclear Iran, may actually persuade Iran that it has nothing to fear and so can outsmart its enemies.

Emanuele Ottolenghi is a senior fellow of the Foundation for Defence of Democracies and author of 'The Pasdaran: Inside Iran's Islamic Revolutionary Guards' Corps' (FDD Press, 2011)