AMSTERDAM - The world's chemical weapons watchdog, which is overseeing the destruction of Syria's toxic arsenal, called on the government of President Bashar Assad to pick up momentum in handing over the remaining chemicals.Syria missed a deadline to transport the most toxic substances out of the country by Dec. 31, loading a first batch of chemicals onto a Danish cargo vessel on Tuesday, a week late.The Syrian government has until the end of March to hand over the so-called first priority chemicals, including around 20 tons of lethal mustard gas, and to the end of June to completely eliminate its chemical weapons program."We are exhorting the Syrian government to intensify its efforts, so we can conclude the critical part of this mission absolutely as fast as the conditions allow," Michael Luhan, spokesman for the Organization for the Prohibition of Chemical Weapons, said on Wednesday."We are happy to see there is finally movement. We hope to see that that movement continues regularly now through the next few weeks, so we can get these chemicals out of the country as quickly as possible."Syria declared 1,300 tons of chemical weapons to the OPCW, which won the Nobel Peace prize last year, and is transporting them by road to the port of Latakia so they can be destroyed abroad.Chemical weapons were likely used in five out of seven attacks investigated by UN experts in Syria, where a nearly three-year-old year civil war has killed more than 100,000 people, a UN investigation found.The most serious attack was on Aug. 21, when hundreds of people died in a sarin gas strike in the outskirts of the capital, Damascus.That attack prompted the United States to threaten to use military force against Assad's regime, which it said was likely responsible.The bulk of the chemicals will be processed on the Cape Ray, a 200-meter (650-foot) U.S. cargo ship, which is being fitted with a portable hydrolysis system to neutralize around 560 tons of the most deadly toxins.The remainder will go to commercial toxic waste processing plants, including one in England.