Washington (CNN) Not so long ago, France was nothing but a lily-livered punch line in Washington.

So it has surprised some to see it emerge as the tough-talking bad cop in nuclear negotiations with Iran.

A decade ago, conservatives loved to mock France as a symbol of weakness, 'effete' liberal internationalism and what they regarded as "Old Europe" appeasement of hostile forces in the Middle East.

But French-U.S. relations have traveled a long way since the days when America's oldest ally was lambasted Simpsons-style as a home for "cheese-eating surrender monkeys" and Capitol Hill menus listed "Freedom Fries."

Twelve years after that estrangement, sparked by Paris's opposition to the Iraq war, France has shifted from being to the dovish left of America on key foreign policy questions to its hawkish right.

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This new trend is playing out in Switzerland, where France is adopting a firmer public line on the deadline-busting nuclear talks with Iran than the Obama administration -- which by comparison looks much more eager for a deal.

While Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif met yet again Wednesday to thrash out an agreement long past its Tuesday midnight deadline, the top French negotiator left and spent most of the day in Paris.

Foreign Minister Laurent Fabius, said on Wednesday that "things have progressed, but not enough" to produce an immediate deal.

"We want there to be an agreement, there's no doubt about that, (but) this agreement can only happen if it is robust and verifiable," he said, speaking in French. A French source said that late Wednesday Fabius headed back to Lausanne, where the talks are taking place.

French skepticism of Iran

Though what France has said behind closed doors at the negotiations remains unknown, Paris is now seen as more skeptical of the chances of a firmly binding Iran deal than the Obama administration, which has invested enormous political capital in the agreement and faces intense opposition from Republicans back in Washington.

In fact, the end-of-the-March milestone seems more rooted in President Barack Obama's need to show progress as skeptics in Congress fight to kill the deal than representing a true inflexion

point in a negotiating process that has as its final deadline June 30.

There are signs that the French believe that Washington could in fact get a better political deal than the one that is currently on the table.

"The French understand the value of time, and essentially they know that the longer this goes on, within reason, the more reasons the Iranians have to give things up," said Atlantic Council senior fellow Nicholas Dungan.

"The French feel that we can ask for an agreement on specifics which the Iranians might be reluctant to give but which the French believe they probably will give in order to get the deal done."

And France isn't just playing the bad cop role for the sake of stiffening negotiations -- it has its own unique view of power politics in the Middle East.

For one thing, it has been burned by Iran before.

Burned by Iran before

Paris has actually been engaging Tehran on its nuclear program for years longer than the U.S., and therefore has had more time to see its expectations dashed. It was part of negotiations with Iran along with Germany and Britain in 2004 and 2005. And it learned hard lessons when it was revealed in September 2009, during a visit to the United States by then-French President Nicolas Sarkozy, that Iran had built an underground uranium enrichment facility at Fordow -- despite previous denials.

Photos: Iran: Key players in the nuclear talks Photos: Iran: Key players in the nuclear talks After arduous talks that spanned 20 months, negotiators reached a landmark deal aimed at reining in Iran's nuclear program, announced on July 14. From left, European Union High Representative for Foreign Affairs and Security Policy Federica Mogherini, Iranian Foreign Minister Mohammad Javad Zarif, Head of the Iranian Atomic Energy Organization Ali Akbar Salehi, Russian Foreign Minister Sergey Lavrov, British Foreign Secretary Philip Hammond and U.S. Secretary of State John Kerry pose for a group picture at the United Nations building in Vienna on July 14. Hide Caption 1 of 10 Photos: Iran: Key players in the nuclear talks U.S. Secretary of State John Kerry has been spearheading negotiations on a possible deal to rein in Iran's nuclear program. Hide Caption 2 of 10 Photos: Iran: Key players in the nuclear talks Kerry, second from left, meets Iranian Foreign Minister Mohammad Javad Zarif, second from right, for talks in Lausanne, Switzerland, on Monday, March 16. At the far left is U.S. Secretary of Energy Ernest Moniz. At the far right is Ali Akbar Salehi, head of Iran's Atomic Energy Organization. Hide Caption 3 of 10 Photos: Iran: Key players in the nuclear talks Iranian Supreme Leader Ayatollah Ali Khamenei meets with environmental officials in Tehran, Iran, on Sunday, March 8. Hide Caption 4 of 10 Photos: Iran: Key players in the nuclear talks Iranian President Hassan Rouhani speaks in September during a news conference in New York. Hide Caption 5 of 10 Photos: Iran: Key players in the nuclear talks Wendy Sherman has been a key U.S. negotiator in the Iran talks. She is the under secretary of state for political affairs. Hide Caption 6 of 10 Photos: Iran: Key players in the nuclear talks Federica Mogherini, foreign policy chief for the European Union, has been representing the Europeans in nuclear talks with Iran. Hide Caption 7 of 10 Photos: Iran: Key players in the nuclear talks Iran's parliament speaker Ali Larijani listens to a question during a news conference in Tehran on March 16. Hide Caption 8 of 10 Photos: Iran: Key players in the nuclear talks Yukiya Amano is director general of the International Atomic Energy Agency, the U.N.'s nuclear watchdog. Hide Caption 9 of 10 Photos: Iran: Key players in the nuclear talks Iran and world powers comprising the P5+1 negotiating team meet in Montreux, Switzerland, on Thursday, March 5. Hide Caption 10 of 10

"The French do not necessarily trust the commitment that the Iranians might actually engage in," said Guillaume Xavier-Bender, a Transatlantic Fellow with the German Marshall Fund of the United States.

"They don't trust that every element will be respected because of their history of negotiation with the Iranians -- they have been deceived multiple times."

That French preoccupation was revealed in an earlier stage of the current round of nuclear talks with Iran that now also include the U.S., Russia and China.

Washington was angered at France's last-minute reluctance to sign on to an interim nuclear deal that was finally agreed to in late 2013.

Back then, Fabius insisted on the toughening of language on Iran's right to enrich uranium and on its plutonium reactor at Arak, changes to a draft deal that Washington later embraced.

There are also broader political and diplomatic forces at work between France and the United States behind the scenes, which, according to both sides, have brought relations to their strongest point in years, the differences over the Iran negotiations not withstanding.

America's most reliable European ally

France has emerged as Washington's most reliable European partner in power projection outside its backyard, better even than Washington's 'special relationship' ally Britain.

A fundamental shift in French foreign policy took place after the Iraq meltdown when Sarkozy took power.

"Some of it was down to diplomatic tactics and some of it was a genuine policy decision," said Dungan, author of a forthcoming book titled "Why France Matters."

"One of the reasons why the U.S. could be suspicious or dismissive of France was that it could say 'the French aren't going to fight,'" he said.

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"Right away on taking office, Sarkozy took a much harder line."

So in 2011, it was the conservative Sarkozy who led the charge on Western intervention in Libya to avert what was seen as a possible massacre by Moamer Gadhaffi's forces in Benghazi and convinced Obama to join in.

The trend continued when the socialist Francois Hollande became president in 2012, only to be embarrassed when Obama climbed down from threats to punish Syria for chemical weapons violations while French pilots were strapped into their cockpits to begin bombing runs.

Nevertheless, France was the first European nation to send its planes into the skies over Iraq to bomb ISIS alongside American jets this fall.

French self-interest in the Middle East

Paris also has a narrow self-interest at play in Switzerland that also shapes its hawkish stance.

It's a longtime member of the nuclear club and any widening of the membership -- and a possible Middle Eastern arms race -- would tarnish its own relative prestige and power.

And there may also be some wounded feelings at play. Though they are under an international umbrella, the Iran nuclear talks have effectively boiled down to a bilateral negotiation between longtime enemies Washington and Tehran -- with Europe partially sidelined.

So France's pride dictates that it is unlikely to accept any outcome that appears imposed by the United States.

But that desire to preserve its own primacy in transatlantic affairs is also the reason, experts said, that France would never totally derail nuclear talks so vitally important to Washington.

Such a move would cause a new rupture in ties with Washington that France has spent much of the last decade trying to mend.