Syria has submitted a new 100-day plan for the removal of its chemical weapons after failing to meet a February 5 deadline, Reuters reported on Friday.

However, the international mission overseeing the operation believes it can be done in a shorter time frame, according to diplomats quoted by the news agency.

The Organization for the Prohibition of Chemical Weapons (OPCW) executive committee met on Friday in The Hague to discuss the joint OPCW and UN mission amid growing international frustration at Syria falling behind on its commitments.

Syria has failed to meet an OPCW deadline of February 5 to move all of its declared chemical substances and precursors out of the country.

Despite the delays, the first batch of chemical weapon materials was moved out of the country in early January, and a second shipment was removed several weeks later.

A third shipment was moved out of the country last week, but the OPCW said last week that Syria had only surrendered 11% of its chemical arsenal.

The final deadline under the OPCW plan is for all of Syria’s declared chemical materials to be destroyed by June 30.

“The Syrian 100 day plan for removal of the chemicals, on which we have been briefed, is not adequate,” Philip Hall, head of the British Foreign Office Counter Proliferation Department, told the OPCW, according to a copy of statement quoted by Reuters.

“We now urge the Syrian authorities to accept the proposals submitted by the Operational Planning Group that provide for removal in a much shorter time frame, without compromising on security,” he said.

A senior UN diplomat, speaking on condition of anonymity, told Reuters the international mission believes the operation can be carried out before the end of March, adding that Syria’s proposed end-May deadline would not leave enough time for the chemicals to be destroyed before the end of June.

The OPCW declined to comment on Syria’s proposal.

The international operation to destroy Syria’s stockpile of deadly chemicals is a joint Russian-U.S. plan that was endorsed by the UN Security Council in September. The resolution was a last-minute measure to prevent an American strike on Syria in retaliation for the regime’s alleged use of chemical weapons in an attack on a Damascus suburb in August that left hundreds dead.

This week, the European Union signed over 12 million euros to the OPCW, to help pay for the dismantling of Syria’s chemical weapons program.

Recently, U.S. Secretary of State John Kerry warned Syrian President Bashar Al-Assad he could face consequences for failing to live up to international agreements on the destruction of his chemical arsenal.