President Barack Obama sat down with Russian President Vladimir Putin for crucial talks on the sidelines of the G20 summit as both countries pledged to eliminate ISIS and end the Syrian war that has fueled its rise.

Their huddle over a coffee table in Antalya, Turkey, on Sunday came after the extremist group claimed responsibility for Friday's horrific coordinated attacks in Paris that left 129 people dead and hundreds injured.

The two leaders, who saw each other for the first time since Russia started air strikes over Syria in September, chatted in a foursome with Obama's national security adviser Susan Rice and a Russian aide.

Their meeting was visible on a television feed provided by the summit's host country but their conversation could not be heard.

The White House says the 35-minute encounter centered on talks to end Syria's civil war and that the two leaders agreed that the country needs a political transition led by Syrians. The transition would be preceded by negotiations mediated by the United Nations and a cease-fire.

The two leaders also discussed the conflict in Ukraine and Obama expressed condolences for the victims in the Russian plane crash in the Sinai Peninsula last month.

President Barack Obama sat down with Russian President Vladimir Putin for crucial talks on the sidelines of the G20 summit. Joining them were Obama's national security adviser Susan Rice and a Russian aide

The White House says the 35-minute meeting centered on talks to end Syria's civil war and that the two leaders agreed that the country needs a political transition led by Syrians

Obama talks with Putin as they arrive for a group photo with other leaders for the G-20 Summit in Antalya

The pair had an informal meeting during the gathering of world leaders. They could be seen talking on TV but it is not known exactly what the pair discussed

The huddle comes as the U.S., Russia and other countries pursue a new diplomatic plan to try to end Syria's civil war

The Russian and US counterparts stand either side of Brazil's President Dilma Rouseff for a group photo

They also discussed a new proposal to end the Syrian conflict and Obama's hope that Russia's airstrikes in Syria will focus on IS, not opposition groups fighting Syrian President Bashar Assad

Reporters were not allowed in for the meeting, which took place during a working lunch for leaders attending the summit.

Obama and Putin both leaned in close to each other as they talked, with the former gesturing expressively with his hands.

During the talks with world leaders, Obama said 'the skies have been darkened' by the attacks in Paris.

He vowed to stand in solidarity with France and aid the effort to hunt down the perpetrators and bring them to justice.

However, he offered no details about what the U.S. or its coalition partners might do to step up its assault against ISIS.

Obama and Putin have long been at odds about whether Assad can maintain a role following that transition.

Obama also renewed his call for Russia to withdraw forces, weapons and support for pro-Russian rebels in Ukraine, the White House said.

Putin's foreign affairs adviser, Yuri Ushakov, told reporters that Putin and Obama had a 'quite detailed conversation,' with Syria taking most of the time. He said they talked about the terror attacks in Paris and other terrorism-related issues.

'Strategic goals related to fighting the ISIL are very close, but tactical differences remain,' Ushakov said.

Obama's run-ins with Putin, his longtime antagonist, are always closely watched affairs, with analysts trying to discern their level of animosity based on body language. On video provided by host country Turkey, the two leaders could be spotted leaning in close to one another and chatting in casual fashion, joined by Obama's national security adviser Susan Rice and a translator.

Although their meeting wasn't scheduled in advance, White House officials had suggested it was likely the two would find time to chat during the two-day summit. The two last met in September in New York during the U.N. General Assembly.

President Barack Obama has pledged to redouble American efforts to eliminate Islamic State and end the Syrian war that has fueled it rise at the G20 summit in Antalya, Turkey

Obama speaks to reporters after meeting with Turkey's President Recep Tayyip Erdogan in Antalya, Turkey

Turkish President Recep Tayyip Erdogan (left) shakes hand with U.S. President Barack Obama during the G20 Leaders Summit welcoming ceremony on Sunday

Obama (pictured left, with Erdogan) is attending the G-20 Summit while on a nine-day foreign trip that also includes stops in the Philippines and Malaysia for other global security and economic summits

Despite the pledge, Obama offered no details about what the U.S. or its coalition partners might do to step up its assault against ISIS

Obama denounced the killing spree on Friday as 'an attack on the civilized world' at the summit of world leaders in the seaside Turkish city of Antalya.

'The killing of innocent people, based on a twisted ideology, is an attack not just on France, not just on Turkey, but it's an attack on the civilized world,' Obama said after meeting with Turkish President Recep Tayyip Erdogan.

In addition to the attacks in the French capital on Friday, ISIS has been blamed for two bombings in Turkey this year that killed around 130 people.

The ISIS threat and Syria's war were already on the line-up for the two days of talks at the summit but they were thrust to the forefront by the elaborately coordinated attacks in the French capital - the most destructive attack in the West that has been blamed on the extremist group.

In a fresh reminder of the group's expanding capacity to wreak havoc, five Turkish police officers were injured on Sunday when a suicide bomber blew himself up during a police raid on a suspected ISIS hideout near the Syrian border.

Turkish security forces also rounded up 20 suspected ISIS militants in and around Antalya in the run-up to the G-20.

But while world leaders have made sweeping condemnations following the Paris attacks, they have struggled to offer concrete proposals for how to escalate the fight or more effectively rein in the group.

When asked by reporters whether Obama would consider additional action against ISIS following the Paris attacks, he declined to tip his hand.

The previous day he had faced criticism for claiming ISIS (also known as ISIL) was 'contained just a day before the shocking attacks in Paris.

Obama denounced the spree in Paris as 'an attack on the civilized world' before setting off for the Group of 20 summit in the seaside Turkish city of Antalya

President Obama arrives with other world leaders for the official family photo during the G20 summit in Antalya, Turkey, on Sunday

In an interview with ABC's George Stephanopoulos, which aired on Friday's broadcast of Good Morning America, Obama had declared that he did not believe the terror group was gaining strength.

'What is true is that from the start, our goal has been first to contain and we have contained them,' he said.

'They have not gained ground in Iraq, and in Syria, they'll come in, they'll leave, but you don't see this systematic march by ISIL across the terrain.'

He was blasted for the comments by social media users – including Republican presidential candidate Donald Trump.

Meanwhile, Obama's meeting with Erdogan came at the start of a nine-day trip to Turkey, the Philippines and Malaysia that has already been largely overshadowed by Friday's attacks in Paris and the related issues of Syria's civil war and the resulting migrant crisis.

Obama said the U.S. stands with Turkey and Europe in the effort to reduce the flow of migrants.

Obama denounced the spree in Paris as 'an attack on the civilized world' at the Group of 20 summit in the seaside Turkish city of Antalya

Erdogan predicted a 'strong message' on fighting terrorism would come out of the summit.

'This terror attack was not just against the French people, it was against the whole of humanity,' Erdogan said.

The summit's host, Erdogan is fresh off his party's impressive victory in Turkey's recent elections - but his relations with Obama have been strained over tactical disagreements about how to push Assad out of power in Syria.

The United States, along with coalition partners, has been bombing ISIS in Iraq and Syria for more than a year with limited success.

Obama has been reluctant to get pulled deeper into the conflict and has ruled out a major U.S. ground offensive. However, he recently authorized sending a few dozen special operations forces into Syria.

Other nations the U.S. views warily, including Iran and Syria, have also bombed the Islamic State, in a dizzying range of militaries piloting the skies above the group's self-proclaimed caliphate.

Cautious U.S. optimism about Russia's involvement quickly soured when the government determined Russian President Vladimir Putin was more focused on targeting rebel groups fighting Syrian President Bashar Assad's government than defeating ISIS.

Putin and Obama, who are now lined up on opposing sides of Syria's bloody civil war, planned no formal sit-downs while both were in Antalya, which is located just a few hundred miles from Turkey's border with Syria. They were expected to cross paths on the sidelines of the summit.

The United States, along with coalition partners, has been bombing ISIS in Iraq and Syria for more than a year with limited success. Pictured: Obama shakes hands with Japan's Prime Minister Shinzo Abe

'It's only possible to deal with the terror threat and help millions of people who lost their homes by combining efforts of the entire global community,' Putin said Sunday as he huddled with leaders of emerging economic powerhouses Brazil, India, China and South Africa.

Obama also scheduled a meeting on Sunday with King Salman of Saudi Arabia, a majority Sunni nation that opposes Assad and is deeply skeptical of Iran's involvement in any solution to the conflict.

One option that emerged in the wake of Friday's attacks was the possibility of France asking for help from its NATO allies.

Only one in its 66-year-history - after 9/11 - has NATO's communal defense obligation been invoked.