UNITED NATIONS — The head of the mission charged with destroying Syria's chemical weapons called Wednesday on President Bashar Assad's government and the international community to ensure that the last 16 containers of dangerous chemicals are immediately removed from the country.

Sigrid Kaag told reporters after briefing the U.N. Security Council that a number of key nations have confirmed that Syria has "legitimate" security concerns about transporting the final 7.2 percent of its declared chemical stockpile to the port of Latakia. She said the joint U.N.-Organization for the Prohibition of Chemical Weapons mission has separate information that security conditions in the contested area not far from Damascus "have been very volatile."

But she said getting the last containers on to Danish and Norwegian ships "is very, very critical" and she called for help from key nations. She said she will return to Damascus in a few days to press for immediate removal of the chemicals from "harm's way."

Kaag reiterated that Syria will not meet the June 30 deadline to completely destroy its chemical weapons. But she said in an interview with The Associated Press that the joint mission is hoping to wrap up and hand over its remaining work to the OPCW "within a finite period of time — count it on one hand in months."

Diplomats say intelligence from several countries, including the United States, indicates that Syria may have hidden some chemical weapons material.

Kaag wouldn't comment on these reports, but she said there were "a number of queries" about Syria's initial declaration of its chemical agents "and a number of member states have expressed their concern."

She said technical experts made two visits to Syria to discuss outstanding issues and would brief the OPCW's executive council on their findings on June 17 at its headquarters in The Hague, Netherlands.

Kaag also said an OPCW fact-finding mission into alleged chlorine attacks in Syria, which was ambushed and briefly held by gunmen in rebel-held territory on May 27, left Syria last Friday.

The international effort to eliminate Syria's chemical weapons was sparked by a chemical weapons attack near Damascus last Aug. 21 that killed hundreds of people. It was blamed on Assad's government, which denied involvement.

Under an agreement brokered by the United States and Russia, the Syrian government is responsible for getting the most dangerous chemicals to the port and destroying the rest inside the country.