U.S. President Barak Obama is stepping up a lobbying campaign for Congressional support of a military strike on Syria after failing to reach agreement Friday with Russian President Vladimir Putin, who vows to back the Mideast country in case of strike.

Obama supposed to address the nation on Tuesday, taking the military action directly to the Americans.

Admitting the early vote of Congress not encouraging, he and his team will exert more efforts on the swayed lawmakers by offering them more classified briefing on the alleged chemical attack in Syria.

Calling it as a "heavy lift," Obama hoped the briefing could convince more skeptical lawmakers and therefore bring more supports for his plan.

"I understand the skepticism. I think it is very important, therefore, for us to work through, systematically, making the case to every senator and every member of Congress. And that's what we're doing," he told reporters in Russia's St. Petersburg.

Congress sources said that there will be a full vote on the military action next week in the Senate while the House may vote within the next two weeks.

Meanwhile, U.S. Secretary of State John Kerry is scheduled to meet with European foreign ministers Saturday to drum up support over Syria issues.

Kerry will meet French Foreign Minister Laurent Fabius Saturday evening for talks on the Middle East, including Syria.

"This meeting will provide an update on the situation in the Near and Middle East, including the situation in Syria and the response to the chemical massacre on Aug. 21," said French Foreign Ministry's spokesman Philippe Lalliot.

In support of the United States, France and nine other countries signed a statement in St. Petersburg calling for a "strong international response" to the alleged chemical attack.

France and the United States are the two main Western countries who push for military action against Syria.

On Friday, French President Francois Hollande said that he would await the UN investigating report on the claimed chemical attacks in Syria before making the final decision.

That could mean French would not involve in any military strikes against Syria before the end of this month.

Hollande also expects to get backing from his European partners on a possible strike, "at least on the political position," he said.

Also on Friday, Putin said that Russia will help Syria in case of an external military attack.

Moscow has been fulfilling its arms contract with Damascus, Putin told a press conference during the G20 summit, adding it will strengthen cooperation with Syria in humanitarian sector, supply humanitarian aid to civilians who were in grave conditions.

Prior to the summit, Putin noted that Russia supplies Damascus with arms, including components of S-300 air defense system, under previous contracts.

According to the Russian president, the allegation of chemical weapons use in Syria is provocation of militants hoping for external support.

It was a provocation by the opposition fighters "who expect assistance from the outside. I mean assistance from the countries that have supported them from the very beginning. This is the essence of this provocation," he added.

Putin reiterated that the use of force against a sovereign state is possible only for the purpose of self-defense or under a UN Security Council sanction.

Kremlin press secretary Dmitry Peskov said earlier that the G20 leaders on Thursday remained different during their working dinner over the settlement of the Syrian conflict, with an equal number of supporting and opposing urgent measures regardless of legitimate international authorization.

Putin said the half-half division over Syria was not correct, naming the United States, Turkey, Canada, Saudi Arabia and France as countries backing military operation against Syria, while Russia, China, India, Indonesia, Argentina, Brazil, South Africa and Italy opposed the possible action, he said.

British Prime Minister David Cameron had advocated a military solution in Syria but its parliament ruled out the option, Putin added.

"The German federal chancellor is also extremely cautious. Germany is not going to get involved into any military operations."

UN Secretary-General Ban Ki-moon also opposed military actions against Syria without a UN mandate, Putin said.

For his regard, Obama said he did not believe UN Security Council support was required.

"Given Security Council paralysis on this issue, if we are serious about upholding a ban on chemical weapons use, then an international response is required, and that will not come through Security Council action," he said.

Washington has held the Syrian government responsible for perpetrating the Aug. 21 attack in the suburbs of Damascus, which U.S. intelligence report claims killed 1,429 people, including 426 children. Moscow is strongly against any military action on Syria without a UN mandate, saying the U.S. proof of chemical weapons use is far from convincing. Endi