The United States has little doubt the Syrian government used chemical weapons against civilians last week, and any decision to open the site to U.N. inspectors was “too late to be credible,” a senior official in the U.S. administration said on Sunday.

“Based on the reported number of victims, reported symptoms of those who were killed or injured, witness accounts, and other facts gathered by open sources, the U.S. intelligence community, and international partners, there is very little doubt at this point that a chemical weapon was used by the Syrian regime against civilians in this incident,” the official told Reuters. …

“At this juncture, any belated decision by the regime to grant access to the U.N. team would be considered too late to be credible, including because the evidence available has been significantly corrupted as a result of the regime’s persistent shelling and other intentional actions over the last five days,” the official said.