The comments made by senior officials came hours after US, United Kingdom and France together launched fresh airstrikes against suspected chemical weapons facilities in the war-torn country.
"While the available information is much greater on the chlorine use, we do have significant information that also points to Sarin use," a senior US administration official told CNN, citing reports from media, non-governmental organisations and other open sources.
"They do point to miosis, constricted pupils, convulsions and disruptions to central nervous systems. Those symptoms don't come from chlorine. They come from nerve agents. It's a much more efficient weapon, unfortunately, the way the regime has been using it, and it's resulted in higher deaths, it resulted in terrible pictures," the official added.
Earlier on Saturday, US Vice President Michael Pence said that Russia is "on the wrong side of the war" while referring to recent strikes on Syria by the US along with Germany and France.
While speaking at the Summit of the Americas in Peru, Pence claimed that "chlorine and nerve agents" were used in the Syrian chemical attack.
Another US administration official said that Syrian President Bashar al-Assad's government was blatantly responsible for the attack, adding that Washington D.C. had evidence such as photographs on the Internet showing the affected people suffering from asphyxiation and experiencing foaming at the mouth.
The officials were adamant that they would continue carrying out airstrikes until and unless the Assad's government deterred themselves from using chemical weapons in the future.
At the United Nations Security Council meeting, the US ambassador to the United Nations, Nikki Haley on Saturday said that Washington D.C. is "locked and loaded" in an event of a chemical attack by Assad.
She reiterated the US commitment to draw a red line by President Donald Trump against the use of chemical weapons, as reported by the Fox News.
Russia, a long-time ally of Syria, earlier proposed a draft resolution condemning the US-initiated strikes of Syria. It was rejected by the UN, as it was only supported by China and Bolivia.
Meanwhile, the US, Britain and France have launched a joint UN bid in order to investigate the earlier chemical weapons attack in Syria, according to media reports.
The three countries also pushed for enforcing a ceasefire to end the airstrikes in the war-torn country, providing for humanitarian assistance and punishing perpetrators, who are responsible for the chemical attacks in Syria.
The Syrian ambassador to the UN Bashar Jaafari said that the US, UK and France had "undermined international peace and security" and demanded the UN Secretariat to give copies of the UN Charter in order to "enlighten themselves, and awaken themselves from their ignorance and tyranny." (ANI)