Russia will keep on supporting Syrian President Bashar al-Assad’s government if the US launches strikes against the Middle East country, President Vladimir Putin said.

‘‘Will we help Syria? We will,’’ Putin told reporters in St Petersburg on Friday after discussing the Syrian issue with US President Barack Obama and other world leaders at the Group of 20 summit in St Petersburg.

‘‘We are already helping them with weapons and we are cooperating in the economic and humanitarian spheres.’’

Putin said on the eve of the forum that Russia may resume deliveries of advanced S-300 anti-aircraft missiles to Syria if Obama carries through on his threat to attack selected targets to punish Assad for allegedly using chemical weapons.

Earlier on Friday, Obama held an unscheduled meeting with Putin, who is Assad’s ally and has questioned US evidence that the Syrian government was behind the chemical weapons attack.

The US President said the discussion was ‘‘very straightforward’’ and focused on their differences on Syria.

Obama said there’s an increasing global consensus that Syria must be confronted over its use of chemical weapons and that he plans to make his case in an address to the American people next week.

‘‘There is a growing recognition that the world cannot stand idly by’’ and ‘‘there needs to be a strong response,’’ Obama said during a news conference at the close of the international summit in Russia.

Discussions over whether to support military action against Syria dominated  dinner for the Group of 20 leaders and overshadowed talks on the global economy and tax policy.

Obama also faces resistance at home, where he has asked the US Congress to authorise a military strike.

Among the leaders at the G-20 meeting, ‘‘a majority’’ is comfortable with the US conclusion that Bashar al-Assad’s regime is responsible for an attack on civilians last month using sarin gas, Obama said.

Russia has blocked action at the United Nations to authorise a military attack against Syria and Obama is seeking to rally support among US allies.

International Backing

So far, only France has indicated willingness to go along with an armed response.

Major economies that Obama is seeking diplomatic support from include the UK, Australia, Turkey and Saudi Arabia.

Obama met at the summit with the leaders of France, China, Japan, Turkey, Brazil and Mexico.

‘‘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,’’ Obama said.

Obama will return to Washington this weekend to continue pressing Congress for authorisation for a Syria attack. He said he plans to deliver an address on September 10 from the White House.

He again stressed that any action would be ‘‘limited both in time and in scope.’’

US lawmakers are asking questions about the size and cost of a military operation that Obama has said would be limited and not involve US ground troops.