Updated

The head of the mission charged with destroying Syria's chemical weapons told the U.N. Security Council on Thursday that Syria can still meet the April 27 deadline to remove all chemical agents from the country but it is becoming increasingly challenging, U.N. diplomats said.

Sigrid Kaag briefed the council by videoconference on the hold up in the Syrian government's shipment overseas of the raw materials for its poison gas and nerve agent program, and the destruction of less potent chemicals inside the country.

U.N. deputy spokesman Farhan Haq said the shipments stopped on March 20. He said authorities informed Kaag's mission that the halt of shipments was due to the deteriorating security situation in Latakia province, where the chemicals are put on ships in the port of Latakia.

Kaag told the council that the Syrian government said it halted the movement of convoys because of worsening insecurity, according to the diplomats, who spoke on condition of anonymity because the briefing was private. But the government informed Kaag's mission on Sunday that it wanted to resume operations "in coming days," they said.

Kaag tweeted after the meeting that a "swift resumption" of chemical weapons transports is "needed alongside continued verification."

The Organization for the Prohibition of Chemical Weapons said in a report to the United Nations last week that the total percentage of chemicals either removed or destroyed inside the war-torn country is 53.6 percent. The report said Syria pledged to remove all chemicals by April 13, except for those in areas "that are presently inaccessible," which face an April 27 deadline.

The international community, shocked by a chemical attack in August that killed hundreds near Damascus, aims to remove and destroy 1,300 metric tons of chemicals by June 30. The August attack was blamed on the government of Syrian President Bashar Assad, which denied involvement.

Haq said the U.N.-OPCW mission "has impressed upon authorities the need to resume movements as soon as possible in order to meet the timelines for complete removal and destruction of Syria's chemical weapons."

Syria's government missed a Dec. 31 deadline to remove the most dangerous chemicals in its stockpile and a Feb. 5 deadline to give up its entire stockpile of chemical weapons. The Assad regime cited security concerns and the lack of some equipment but has repeated that it remains fully committed to the process.

Syria's U.N. Ambassador Bashar Ja'afari told reporters that opposition fighters "are still shelling the port of Latakia."

"They are seeking to create a catastrophe," he said. "They want to embarrass the government, show it's incapable" of meeting the deadline.

At the Security Council meeting, U.S. Ambassador Samantha Power said insecurity should be a reason to speed up removal, not an excuse for delay, the diplomats said.

She noted that two-thirds of the most dangerous chemicals are still in Syria, they said.

Kaag said Syrian authorities have continued packing and loading chemicals on three sites, and 72 containers are ready to be removed, the diplomats said.

Once this is done, approximately 90 percent of the deadliest chemical agents will have been removed, Kaag told the council, according to the diplomats.

Assuming the removal operations restart immediately, Kaag said the removal and destruction of all chemicals could be achieved by the June 30 deadline, the diplomats said.