Washington blames Russia's ally, Syrian President Bashar Assad, while Moscow says Syrian rebels are responsible.
After a day of discussions with US Secretary of State Rex Tillerson, Russian Foreign Minister Sergey Lavrov said the former Cold War foes agreed a UN probe of events in northern Syria on April 4 was necessary.
More than 80 people were killed in what the US has described as a nerve gas attack that Assad's forces undoubtedly carried out.
Russia says rebels dispersed whatever chemical agent was found, which the Trump administration calls a disinformation campaign.
The news conference came after Russian President Vladimir Putin met the top American diplomat for almost two hours to see if they could rescue relations between the world's mightiest military powers.
Russia's alleged meddling in the US presidential election also hovered over the first face-to-face encounter between Putin and a Trump administration Cabinet member.
"There is a low level of trust between our two countries," Tillerson said candidly.
He said working groups would be established to improve US-Russian ties and identify problems. He said the two sides would also discuss disagreements on Syria and how to end the country's six-year civil war.
The most immediate dispute concerned culpability for the chemical weapons, though broader disagreements over everything from Ukraine to Russia's support for once-fringe candidates in European elections are among other sore points.
Steeped in geopolitical intrigue, the meeting between Putin and Tillerson wasn't formally confirmed until the last minute, following days of speculation about whether the Russian would refuse to grant the former oil executive an audience.
Putin's decision to host Tillerson signaled Moscow's intent to maintain communication with the US even as the countries bash each other publicly in louder and louder tones.
The men know each other well from Tillerson's days as Exxon Mobil CEO. Putin had even granted Tillerson a friendship honor. (AP)