U.S. President Barack Obama and Russian leader Vladimir Putin may discuss Syria on the sidelines of a regional summit in Bali next week, a top Kremlin official said Thursday.

Although Obama is yet to confirm his attendance at the October 7 Asia-Pacific Economic Cooperation (APEC) meeting because of a budget crisis back home, Putin's foreign policy adviser said both Moscow and Washington were getting ready for the talks.

Russian investigators on Wednesday formally charged two of 30 detained Greenpeace campaigners for piracy over an open-sea protest against Arctic oil drilling, an activist said.

"The first two activists have been charged with piracy," Mikhail Kreindlin, a representative of Greenpeace, told Agence France Presse. "These activists are from Brazil and Britain."

A patriotic Russian group on Tuesday called for President Vladimir Putin to be awarded the Nobel Peace Prize for his Syria diplomacy, claiming he was more deserving of the award than laureate U.S. President Barack Obama.

A group that lists senior Russian officials among its members announced at a news conference that it had written to the Nobel prize committee backing Putin for the prize awarded to Obama in 2009.

Russian President Vladimir Putin said Wednesday that 30 Greenpeace activists arrested in Russia over their open-sea protest in the Arctic were not "pirates" but they did break the law.

"I do not know the details of what has happened but it's completely obvious that of course they are not pirates," Putin told an international Arctic forum in the far northern city of Salekhard in televised remarks.

Russian President Vladimir Putin on Monday called any possible foreign military intervention against Syria a form of "aggression" that would rattle the entire region and contravene international law.

Putin told a summit of an ex-Soviet security group that he was grateful for its decision to support Moscow's refusal to sanction strikes against President Bashar Assad's regime for its alleged use of chemical weapons.

Russian President Vladimir Putin said Thursday that he could run for a fourth presidential term in 2018. If he does and wins, that would keep him in power for about a quarter century and make him the nation's longest-serving leader since Josef Stalin.

Putin, who served two consecutive four-year terms starting in 2000, became prime minister in 2008 to observe a constitutional limit of two consecutive terms. He remained in charge as prime minister, with his loyal associate, Dmitry Medvedev, serving as a placeholder.

Russian President Vladimir Putin said Thursday that his friend, Italy's convicted former premier Silvio Berlusconi would not have gone on trial for sex with a minor if he was gay.

"Berlusconi is on trial for living with women, but if he were a homosexual, nobody would dare touch him," Putin said during a discussion with international experts and journalists at the Valdai Club in the northwestern Novgorod region.

Russian President Vladimir Putin said Thursday he was confident but not 100 percent sure that Syria would carry out its commitments to destroy its chemical weapons stockpiles under a Russia-U.S. agreement.

"Will we manage to carry it through? I can't say 100 percent, but all that we have seen recently, in the last few days, inspires confidence that it is possible and that it will be done," Putin said at a meeting of the Valdai international discussion club with Western politicians and journalists in the northwestern Novgorod region.

U.S. Senator John McCain penned a blistering column for Russian media, telling the Russian people that their President Vladimir Putin is a dissent-quashing tyrant who "doesn't believe in you."

The senior U.S. lawmaker, the 2008 Republican presidential nominee, accosted Putin and his associates for rigging elections, imprisoning and murdering opponents, fostering corruption and "destroying" Russia's reputation on the world stage.

President Vladimir Putin on Friday won the support of Iran and China at a regional summit on Russia's initiative for Syria to hand over its chemical weapons, which he said had proved the "serious intentions" of the Damascus regime.

Putin attended the summit of the Shanghai Cooperation Organization (SCO), a regional security group sometimes seen as an eastern counterweight to NATO, in Kyrgyzstan a day after President Bashar Assad said he supported the Russian plan.