Russian President Vladimir Putin says he does not rule out supporting a U.N. authorization of military force against Syria if there is proof government forces used chemical weapons against civilians.
He told the Associated Press and Russian television that the United States should present "convincing" evidence to the U.N., and warned the U.S. against taking military action without U.N. approval.
Putin also said Russia has suspended the delivery of S-300 surface-to-air missile components to Syria, but would reconsider if steps are taken that "violate international norms."
Russia is hosting the G20 summit later this week in St. Petersburg, where Syria is expected to be high on the agenda.
U.S. President Barack Obama has been seeking domestic and intenational support for taking action against Syria. He is stopping in Stockholm for a one-day visit before flying on to Russia.
Photo Gallery: Latest Images from Syria
This citizen journalism image provided by Edlib News Network shows anti-Syrian regime protesters hold a poster depicting U.S. President Barack Obama during a demonstration in Kafr Nabil, Idlib province, Sept. 20, 2013.
Children sit along a damaged street filled with debris in the besieged area of Homs, Sept. 19, 2013.
Debris is seen on the ground after what activists said was shelling by forces loyal to Syria's President Bashar al-Assad in the al-Myassar neighborhood of Aleppo, Sept. 19, 2013.
An injured man walks along a street after what activists said was shelling by forces loyal to Syria's President Bashar al-Assad in the al-Myassar neighborhood of Aleppo, Sept. 19, 2013.
This citizen journalism image provided by The Syrian Revolution against Bashar Assad shows a Syrian military tank on fire during clashes with Free Syrian army fighters in Joubar, a suburb of Damascus, Sept. 18, 2013.
A member of the Shohadaa Badr Brigade, which operates under the Free Syrian Army, stands in shooting position behind sandbags in Ashrafieh, Aleppo, September 17, 2013.
Free Syrian Army fighters walk through rubble inside the old city of Aleppo, Sept. 16, 2013.
A Free Syrian Army fighter carries his weapon as he stands on rubble of damaged buildings in al-Aseela neighborhood near Aleppo's historic citadel, Sept. 13, 2013.
In this citizen journalism image provided by the United media office of Arbeen, a Syrian protester chants slogans during a demonstration in Arbeen, a suburb of Damascus, Sept. 13, 2013.
Meanwhile, a key U.S. Senate committee could vote as early as Wednesday on a measure authorizing U.S. military force. Leaders of the Foreign Relations Committee agreed late Tuesday on details of the plan that would give Obama authority to order limited strikes against Syrian military targets for 60 days. He could extend the window by another 30 days under certain conditions. The resolution would not authorize the use of ground troops.
It states military action must be aimed at deterring and preventing Syria from carrying out future chemical weapons attacks. The measure would also require Obama to present a strategy for bringing a political resolution to the Syrian crisis.
The resolution must clear the committee and gain approval in the full Senate and House of Representatives before taking effect.
France also says it has evidence Syrian forces were responsible for the deadly attack near Damascus last month. The country's parliament is debating a possible military response in a session Wednesday, though French President Francois Hollande does not need lawmakers' approval to act.
Syria has denied using chemical weapons, alleging it was the rebels who deployed them.
Congressional leaders support Obama plan
Tuesday in Washington, John Boehner and Nancy Pelosi, the Republican and Democratic leaders in the House, expressed their support for President Obama's plan. Others in Congress remain leery of approving military force.
Secretary of State John Kerry told the Foreign Relations Committee he has no doubt that U.S. inaction on Syria would lead to a greater war and more use of chemical weapons.
He said it is beyond any reasonable doubt that President Bashar al-Assad's government used chemical weapons on civilians in the attack last month that killed more than 1,400 people near Damascus.
Kerry and Defense Secretary Chuck Hagel are due to appear Wednesday before the House Foreign Affairs Committee to discuss Syria.