As the drive to reach an accord with Iran on its nuclear programme heads towards a March 31 deadline, France is digging into its role as chief hawk -- a position inclined to annoy US allies, but not likely to scuttle an eventual accord, diplomats say.

The French hard-line among its US, British, Chinese, Russian and German partners to hammer out a nuclear agreement with Tehran is rooted in ideological, historical, and even personal concerns that tend to stiffen as Paris recognises Washington's increasing pragmatism in seeking to conclude a deal swiftly.

"France has taken the opposite path to that of the United States, which changed strategies with the arrival of Barack Obama," said Bernard Hourcade, an Iran specialist at the National Centre of Scientific Research, who says France's current Socialist-led government adopted and defends the wary, intransigent stance towards Iran set down by previous conservative president Nicolas Sarkozy.

"Paris has clearly made the choice of going with Gulf oil monarchies and with a conservative stability" in the region, and frontally opposing Iranian interests and influences that Paris blames for violence and turmoil in Syria, Lebanon and Iraq, Hourcade said.

- 'Matter of degrees' -

It was that scepticism vis-a-vis Teheran that led France to initially block the November 2013 accord between Iranian and US diplomats -- one that French officials rejected at the 11th hour for granting Iran too many concessions in the zeal to come away with an interim agreement sooner.

Though a tightened deal was signed 15 days later, US officials are now closely watching their French partners for signs Paris might again veto an agreement hammered out as the March 31 deadline for a framework treaty looms.

"The French won't take the risk of ruining negotiations. The global powers are all in agreement on the main issues," said Francois Nicoullaud, a former diplomat posted to Tehran in the 2000s, and specialist on non-proliferation.

"Beyond that, it's a matter of degrees, which Paris will be seeking to push as far as possible," he added.

There are reasons beyond policy continuity on Iran between otherwise contrasting French governments that explain Paris' tough stand in the talks.

For starters, French diplomats overseeing nuclear talks with Iran are from the neoconservative school, and as such are particularly suspicious and inflexible in dealing with Teheran.

- 'Absolutely no trust -

Meanwhile, current French Foreign Minister Laurent Fabius served as prime minister from 1984 to 1986 -- a period when Iranian actions created particularly tense relations between Paris and Tehran.

During that brief span, Iran was blamed as ultimately responsible for attacks committed in France and hostages snatched by Hezbollah in Lebanon, while Tehran fumed at Paris' support for Saddam Hussein in the disastrous Iraq-Iran war.

"Fabius still has a terrible impression of the Iranians, and has absolutely no trust in them," a French diplomat confided.

Another concern, people following the negotiations note, is France's desire for its expertise in nuclear issues to be duly taken into account in shaping a deal -- it sees itself as the world's "guardian of the non-proliferation temple."

Yet in the end, diplomats and specialists concur, France's effort to secure the most restrictive nuclear agreement possible with Tehran will not trump the dominant roles the US and Iran will play.

"At the end, it will all revolve around two big negotiators, the United States and Iran," a European diplomat noted. "Everything will depend on their ability to take a leap of faith, which is a fantastic and fascinating gamble."

However, outside factors seeking to prevent that may yet prove more disruptive than any French qualms with an agreement.

"The problem in this negotiation is it is really on a razor's edge, and there are a lot of people who will do anything to sabotage a deal," said Hourcade, citing the Iranian old guard, conservative US legislators, Gulf countries, and Israeli Prime Minister Benjamin Netanyahu as examples.

"Just a few symbolic details, three centrifuges more or less, could mean failure," Hourcade warned.