Syria must move faster to remove its deadly chemical weapons stockpile and meet the June 30 deadline set for destroying its arsenal, the UN Security Council demanded Thursday.

The 15 member nations "call upon the Syrian Arab Republic to expedite actions to meet its obligations," the council's president for the month, Lithuania's UN ambassador Raimonda Murmokaite, told reporters..

The chemical weapons must be transported to the Syrian port of Latakia "in a systematic and sufficiently accelerated manner," Murmokaite insisted, after summarizing the closed door discussions the council held earlier Thursday with Sigrid Kaag, who is tasked with coordinating Syria's disarmament.

Syrian President Bashar al-Assad has pledged to eliminate Syria's entire chemical weapons arsenal by the end of June or face sanctions, including the possible use of force.

Less than five percent of the deadly stockpile has been removed from Syria, according to Washington, and Damascus has just missed another key deadline.

Rejecting in part Damascas' explanations for the delay, the Security Council noted that, according to UN assessments, "Syria has sufficient material and equipment" as well as "substantial international support" to transport their chemical weapons stockpile in line with deadlines.

The Lithuanian ambassador "welcomed the cooperation" between the government and the joint mission by the United Nations and Organization for the Prohibition of Chemical weapons led by Kaag.

The council's members "remain committed to seeing the 30 June deadline met," Murmokaite concluded.

Delay is 'not insurmountable'

Earlier Thursday, diplomats said Kaag had told the council that Syria's delay in destroying its chemical arsenal was "not insurmountable" but Damascus must sharply step up the pace to meet its deadlines.

"As the Council is aware, the intermediate timeline objectives have not been met. Syria is at critical juncture," diplomats quoted Kaag as warning the council.

Western powers have expressed concern at the slow pace of the handover, fearing that Assad is playing for time, but Russia, Syria's key ally on the UN Security Council, called for calm.

"Things are moving along," Russian ambassador Vitaly Churkin said on Wednesday.

"We are confident this project is going to be accomplished in a timely manner and these chemicals are going to be destroyed."

But, even before Kaag's briefing, envoys remained skeptical.

"We feel the times for excuses has run out," British ambassador Mark Lyall Grant said as he arrived.

"There needs be proper arrangements for accelerating the process of getting the chemicals out of Syria."

The United States says only about four percent of Syria's declared arsenal has left the port of Latakia so far -- far less than the 700 tonnes the country was supposed to dispose of by the end of 2013.

In addition to the 700 tonnes of the most deadly agents that should have been dealt with last year, another 500 tonnes of less deadly "category two" chemicals should have left by Wednesday.

In fact, only two small shipments have left Latakia, on January 7 and 27. Another 120 tonnes of isopropanol is due to be shipped before March 1.

The UN Security Council last year backed a US-Russian deal to destroy Syria's vast chemical arsenal after chemical attacks near Damascus that Washington blamed on the regime.