Government and rebel forces are blaming each other for an alleged chemical strike that killed and injured several people in central Syria April 11.
Sources differ on the victim total: Opposition groups say six people died in the attack, while state TV said two people were killed and more than 100 injured.
Online videos show victims, including children, gasping for air. Experts say the symptoms displayed are consistent with a chemical attack.
"We will do everything in our power to establish what has happened, and then consider possible steps. ... We weren't just removing for removing's sake, it was to avoid use. So we will have to look at policy options," U.S. Ambassador to the U.N. Samantha Power told ABC's "This Week."
"The president has made very clear how alarming he finds chemical weapons use, how outrageous he found it. That's why he put the credible threat of military force on the table," Power said.
"That's why we've been able to destroy and remove more than half of Syria's chemical weapons up to this point," she continued. "But certainly the point of what we've done so far is to prevent further use."
Power said the United States is investigating the situation and considering an appropriate response.
Meanwhile, international groups are still working on dismantling the country's chemical weapons stockpiles.