Former Obama administration official Tony Blinken said over the weekend that the U.S. "always knew" the 2013 agreement with Russia and Syrian President Bashar al-Assad did not clear all chemical weapons out of Syria.
Blinken, the former deputy secretary of state and former deputy national security adviser under former President Barack Obama, spoke with the New York Times for an article published Sunday.
"We always knew we had not gotten everything, that the Syrians had not been fully forthcoming in their declaration," Blinken said, despite the Obama administration frequently claiming success for getting all the chemical weapons out of Syria.
The United States brokered a deal with Russia and Syria in 2013 that was designed to get rid of the Assad regime's chemical weapons stockpile.
But last week on April 4, Assad launched a chemical attack that struck the rebel-held town of Khan Sheikhoun in northern Syria. The attack killed nearly 100 noncombatants, including children.
In 2014, former Secretary of State John Kerry claimed the deal that the Obama administration stuck with Damascus and Moscow resulted in the removal of "100 percent" of its chemical agents.
Susan Rice, Obama's national security advisor, has also praised the deal's success.