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Zach Coleman, Special for USA TODAY

World leaders have converged on St. Petersburg for Group of 20 talks on international tax treaties, banking reform and the global economy, but the prospect of military action in Syria was threatening to overshadow the economy-focused summit as President Obama arrived in the northern Russian city Thursday.

Syria is not on the formal agenda for the two-day event. However, on Thursday, a United Nations spokesman said that Lakhdar Brahimi, special envoy of the U.N. and Arab League on Syria, would travel to St. Petersburg to rally efforts to convene a peace conference in Geneva.

"A political solution is the only way to end the bloodshed in Syria," U.N. Secretary General Ban Ki-moon said.

Russian President Vladimir Putin has warned that any military intervention against the regime of Syrian President Bashar al-Assad without the express consent of the U.N. would amount to an act of "aggression."

But Dmitry Peskov, a spokesman for Putin, told the Voice of Russia that the Russian president does not plan to meet Brahimi.

Putin also said this week he doesn't exclude supporting U.N. action - if it's proven that the Syrian government used poison gas on its own people.

On Wednesday, the Senate Foreign Relations Committee voted to authorize President Obama to use limited force against Syria, after adopting amendments from Sen. John McCain designed to urge Obama to "change the military equation on the battlefield."

SYRIA:Senate committee approves Syria attack resolution

Still, men at the forefront of the geopolitical standoff over Syria's civil war will be in the same room for meetings Thursday and Friday: President Obama, Russian President Putin, French President Francois Hollande, U.N. Secretary-General Ban, Turkish Prime Minister Recep Tayyip Erdogan and Saudi Prince Saun Al Faisal al Saud, among others.

The world's unemployed and impoverished may therefore get short shrift at this summit, though activist groups are pleading with leaders to join forces to tackle corruption and tax-avoiding corporations, hoping that stabilizes and better distributes economic growth.

China, too, voiced its disinterest in an attack. "Military action would have a negative impact on the global economy, especially on the oil price," Chinese Vice Finance Minister Zhu Guangyao told reporters at the summit.

Away from Syria, one of the key items up for discussion is on a pact on combating tax evasion and tax avoidance.

The U.S. and several European countries are pushing for an agreement on sharing information to catch tax dodgers which is likely to build on the U.S. Foreign Account Tax Compliance Act. The law, passed last year, requires foreign financial institutions to report to the U.S. about American account holders.

G-20 members are also taking aim at the kind of profit shifting loopholes that Vodafone Group used to minimize the tax bill on the $130 billion sale of its stake in Verizon Wireless. Progress on these issues has been helped by a shared interest in shoring up government revenue, said Yves Tiberghien, a professor at the University of British Columbia.

The G-20 leaders will also take up a proposal to improve oversight of "shadow banks" - hedge funds and other non-banks that now account for a large proportion of lending activity.

G-20 nations - including China, France, Brazil, Canada, Australia, the U.S. and others - represent two-thirds of the world's population, 85% of its GDP and its leading armies.

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