(CNN) Senior US officials expressed confidence Saturday that both chlorine and sarin gas were used in Syria's alleged chemical weapons attack on the Damascus enclave of Douma last week -- a conclusion that went a step further than Vice President Mike Pence did in his remarks earlier Saturday.
"While the available information is much greater on the chlorine use, we do have significant information that also points to sarin use," a senior administration official said on a call with reporters, citing reports from media, nongovernmental organizations 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 comments come a day after the United States launched targeted airstrikes against suspected chemical weapons facilities in Syria in coordination with the British and French.
Earlier Saturday, Pence held off from expressing a final judgment about whether sarin gas was deployed in the chemical weapons attack.
"Chlorine and possibly nerve agents were used," Pence said during his address at the Summit of the Americas in Peru.
Another administration official laid out evidence on Saturday for the United States' conclusion that Syrian President Bashar al-Assad's government was behind the chemical weapons attack; that included eyewitness accounts of Syrian government helicopters circling the site of the attack on April 7 and high-resolution photos that "clearly" documented asphyxiation and foaming at the mouth.
"Assad has established himself as a user of chemical weapons" from past attacks, the official added.
Another official said, "We have incontrovertible evidence from the photos" that chemical weapons were used and it was "clear to the international community."
The administration maintains that it "exhausted every avenue in the international community" for diplomacy and sanctions before launching the missile strike, and that the President and allies felt the appropriate response was military action.
US officials said they hope the strike will serve to deter Syria's government from using chemical weapons in the future.
"If this step does not succeed, we will be prepared to act again," an official said on the call, echoing what other top administration officials emphasized on Saturday.
Whether or not that happens is up to Syria and also Russia, the officials said.
"We want to have an engagement with Russia that leads to greater peace, security and stability in the world, including in the Middle East and including in Syria," an official said.
Russia put forward a draft resolution at an emergency United Nations Security Council meeting Saturday morning to condemn the US, French and British military action, but the resolution failed.
"It's a sad day for the world, the UN, for its charter -- which was blatantly, blatantly violated -- and for the Security Council which has shirked its responsibilities," Russian Ambassador Vassily Nebenzia said.
Syrian ambassador to the United Nations Bashar Jaafari said the US, UK and France had undermined international peace and security, and asked the Secretariat to distribute copies of the UN Charter to the three nations in order to "enlighten themselves, and awaken themselves from their ignorance and tyranny."
On Saturday, the Trump administration said the strikes accomplished three strategic goals: to deliver a direct response to the chemical weapons attack, to hold Assad responsible for his actions, and to present a deterrent on chemical weapons use in Syria and elsewhere in the future.
One official cautioned, however, that US intelligence assessments indicate Assad still has chemical weapons in Syria.
Compared to strikes that President Donald Trump launched against a Syrian air base after a previous chemical weapons attack on civilians nearly one year ago, last night's action was "more robust in terms of military action" because it was an allied, as opposed to unilateral, strike that targeted alleged chemical weapons infrastructure and is meant to be part of a sustained effort, an administration official said.
The administration maintains that the airstrikes were not connected to the campaign against ISIS in eastern Syria. When asked if the Syrians could have repositioned their alleged chemical weapons resources to protect them from the impending strike, one official said they believed there were "things in these buildings that were not able to be moved."
Officials would not describe Trump's decision-making process in much detail or the options presented, but they did say there were week-long deliberations. Trump and his entire national security team consulted closely with allies, with one senior official saying, "I would say it's rare for more than a few days to go by that the President doesn't have a consultation with President Macron or British counterparts."