The push to bring warring sides together is becoming ever-more pressing in a conflict that has claimed more than 94,000 lives, amid reports of "horrific" rights violations and mounting evidence that chemical weapons are being used.
In Brussels, meanwhile, 27 European Union foreign ministers struggled to hammer out a compromise in a lengthy meeting aimed at deciding whether to supply weapons to Syria's rebels when an arms embargo expires this week.
Kerry and Russian Foreign Minister Sergei Lavrov met in a Paris hotel to advance the initiative for an international peace conference, and the two will later be joined by French Foreign Minister Laurent Fabius for dinner.
The US secretary of state will brief Lavrov about a recent Friends of Syria meeting in Jordan, at which the 11 ministers of the core group told Syrian President Bashar al-Assad that refusing to negotiate was not an option.
Also Read
The proposed conference is being spearheaded by Russia and the United States and has been dubbed "Geneva 2" after a similar meeting last June produced a peace roadmap that was however never implemented.
But with the much-publicised involvement of Hezbollah threatening to pull Lebanon deep into the conflict, the talks are becoming increasingly pressing.
Fabius today said there were "mounting suspicions" that chemical weapons were being used in Syria, and UN human rights chief Navi Pillay decried the "horrific" level of rights violations.
The opposition umbrella group, which is currently locked in fractious talks in Istanbul to choose a new leadership, is suffering from deep divisions that some members say are due to regional bids for influence.
EU ministers, meanwhile, were locked in long talks over whether to roll over a wide-ranging package of sanctions against Assad's regime, including a blanket arms embargo, which failing an agreement lapses on Friday.
Britain and France, with some support from Italy and Spain, want the arms embargo lifted to enable rebels to get weapons and help tilt the military balance on the ground, but other countries such as Germany and Sweden are opposed to this.