BEIRUT — The United States accused the Syrian government Thursday of using stalling tactics to delay efforts to remove and destroy chemical agents, an indication that the international community’s patience is wearing thin.

The comments, delivered by the U.S. representative to the international chemical weapons watchdog, marked some of the strongest public criticism of Syria’s commitment to relinquish its chemical stockpile.

Syria agreed to surrender its arsenal after a deadly chemical attack in August on a rebel-held suburb of Damascus raised the threat of punitive U.S. missile strikes. President Obama has touted the agreement as a victory and a major policy achievement for his administration on Syria’s intractable civil war.

The Organization for the Prohibition of Chemical Weapons is leading the mission to eliminate Syria’s 1,300-metric-ton stockpile by a June 30 deadline.

Under the OPCW’s tight timeline, the most toxic chemicals in Syria’s arsenal were to have been removed from the country by Dec. 31, but that deadline was missed due to poor security amid Syria’s raging civil war and other factors. So far, just two small consignments of chemicals have been shipped out.

“The effort to remove chemical agent and key precursor chemicals from Syria has seriously languished and stalled,” Robert Mikulak told the OPCW’s 41-nation executive council.

Mikulak, the U.S. representative to the OPCW, acknowledged that the timeline for the removal of Syria’s most dangerous chemicals was ambitious, but he expressed frustration that a month after the deadline “only 4 percent” of the chemicals has been removed “and the Syrian government will not commit to a specific schedule for removal.”