* Seeks to "shock" EU's moribund foreign policy
* Brexit vacuum, German slowdown gives him openings
* Frustration in Brussels at being bypassed
* EU sees contradictory Macron approach on Russia
By John Irish and Robin Emmott
PARIS/BRUSSELS, Sept 17 (Reuters) - Just as the United States is seeking less frosty ties with the new leaders of the European Union, French President Emmanuel Macron has seized the helm of European diplomacy, filling a vacuum left by a distracted Britain and a weakened Germany.
The high-stakes strategy, in which Macron has bypassed London, Brussels and Berlin since August to try to defuse a U.S.-Iran standoff and mend EU ties with Russia, is part of a bid to boost French influence across EU affairs, diplomats say.
While he has won praise for trying to resolve chronic global crises, his approach is alienating European allies by eroding a painstakingly built, multilateral EU system, adding to confusion abroad about who is really running Europe, diplomats say.
"We will speak to whoever is in charge, and if that's Macron, fine," Gordon Sondland, U.S. Ambassador to the European Union, told Reuters. "But if I were the Czech Republic or Italy, I'd ask whose interests he is putting first."
Prime Minister Boris Johnson is preoccupied by Britain's decision to exit the EU, while Germany's Angela Merkel is on her way out amid a slowdown of the EU's biggest economy.
Against that backdrop, Macron's hosting of the annual G7 summit in the French coastal resort of Biarritz last month underlined his burgeoning diplomatic ambitions.
Macron held a private lunch with Donald Trump and, with the latter's blessing, allowed Iran's foreign minister to spend a few hours in Biarritz and spoke with Iranian President Hassan Rouhani, all in hopes of coaxing direct U.S.-Iranian dialogue.
None occurred, though Macron later declared Rouhani was open to meeting Trump, possibly at the annual United Nations General Assembly that opens this week in New York.
But diplomats said Macron's diplomacy with the Iranians took Britain and Germany, France's partners in the now unravelling 2015 nuclear deal with Tehran, by surprise.
In early September, Macron sent his foreign and defence ministers to Moscow to reset strained EU relations with Russia without telling the bloc's Brussels-based foreign policy branch beforehand, three EU diplomats said.
The Moscow venture came days after U.S. Secretary of State Mike Pompeo flew to Brussels to meet the incoming leaders of the EU, including new foreign policy chief Josep Borrell, a more seasoned diplomat with whom Washington says it wants to work.
"The (2016) Brexit vote has caused British foreign policy to shrink dramatically. When Emmanuel Macron swept into power in May 2017, the theory was that Paris and Germany would form a tight alliance in the foreign policy realm," said Jalel Harchaoui, research fellow at the Clingendael Institute.
"In reality, Merkel's Germany...has largely neglected international diplomacy. Meanwhile, Macron's France, hailed as a beacon of liberalism, has time and time again ignored the EU."
"ELECTRIC SHOCK" TREATMENT
France says it is concerned that while the EU wields "soft power" as the world's biggest aid donor, the 28-nation bloc has been unable to respond effectively as a whole to multiple crises including in Ukraine, Syria and Yemen.
But in Libya, where chaos has reigned since the 2011 fall of Muammar Gaddafi, Macron's go-it-alone approach backfired.
France organised two summits trying to bring warring Libyan factions together, but failed to make progress and angered Italy, which saw the move as French intervention in its traditional geographic backyard.
Tensions between Paris, Berlin, Rome and Brussels mean EU foreign policy could fray further as Europe is evolves into a theatre of strategic rivalry between the United States and China, with Russia as Beijing's junior partner, diplomats warn.
Some Paris-based foreign diplomats are excited by the new direction of European diplomacy. They feel they are better off cultivating closer ties with Macron's government than with Brussels as he pursues robust diplomatic initiatives.
"Europe needed electric shock (treatment). Macron gets us involved now on global matters, whereas before we got ignored. We see Paris as the place to go to first in Europe to get things done," said a Western diplomat based in Paris.
In his annual speech to the Paris-based diplomatic corps in August, Macron repeated 18 times the need for audacity in French diplomacy, and for France to fully play its role as a "balancing power" in a world dominated by China and the United States.
"Today, in Europe, nobody has that vitality and nobody has made the strategic and human investment that we have. And that is our fundamental point: to influence things," Macron said. "We need this strategy of audacity."
DE GAULLE REDUX?
EU diplomats say it suits Germany to let Macron take the lead on averting conflict with Iran as Berlin is loath to upset Iran's foe Israel for historical reasons, or appear to confront Trump, with whom the Germans have a fraught relationship over trade, natural gas contracts with Russia and defence spending.
But there is a contradiction in Macron's approach.
He never tires of championing the European Union but at the same time fails to coordinate through EU channels on strategic objectives, diplomats and former officials said.
"What is striking is that Macron is like former presidents Sarkozy and Chirac. They want to appear to be on the global stage. It's the same reflexes as in the past," said a former senior French administration official.
Some officials say Macron resembles Charles de Gaulle, the founder of modern France who sought an international profile for France that was neither pro-American nor fundamentally European. Macron keeps a copy of De Gaulle's memoirs on his desk.
"On the one hand, the focus is Europe, Europe and more Europe, but on the other hand when we're talking about the big strategic policies, he completely forgets Europe," said the former official, who continues to advise the government.
Nowhere is that more apparent than on Russia. Macron's outreach to Moscow echo those of his predecessors, reflecting the French public's traditional esteem for Russian culture.
But European partners more geographically exposed to perceived Russian attempts to weaken the EU, in part through support for eurosceptic nationalists, are not amused.
"It goes against the Poles, the Scandinavians, and gives the general impression that we're not interested in Europe," said one French diplomat.
"There's also a fundamental contradiction. How can you be the man fighting the (anti-EU) populists in Europe, while giving the impression that all of Moscow's worst actions are swept under the carpet?"
French officials deny that Macron is circumventing his allies, arguing that Paris has always kept the EU abreast of its efforts and that dialogue with Russia is in Europe's interest.
They say that if there was a breakthrough on Ukraine's conflict with pro-Russian separatists, with a possible diplomatic summit in the coming weeks, this would build trust with fellow Europeans.
"The idea is to start a conversation on our priorities on the future European security architecture," a senior French diplomat said. (Reporting by Robin Emmott and John Irish Editing by John Chalmers and Mark Heinrich)