Syria has relinquished only 11 percent of its chemical weapons in three shipments and is on track to miss a politically-loaded midyear deadline to completely destroy the toxic stockpile, sources told Reuters on Friday.

Syria should already have handed over the 1,300 tonnes of toxic chemicals declared to the Organisation for the Prohibition of Chemical Weapons (OPCW), the body overseeing the process with the United Nations under a Russian-American deal.

A third shipment this week contained 54 metric tonnes of hexamine, a raw material for explosives, bringing the total shipped so far to a bit more than 140 tonnes, three sources at the OPCW said.

That includes only about 5 percent of the most toxic priority chemicals, the sources said.

“Let’s be honest, the important materials have not yet been brought, except a little consignment at the beginning. That means we are well behind schedule,” one source said.