Secretary of State John Kerry said in Germany that Syria and the international community had agreed to a plan and a timetable for the project, and Damascus was obligated to follow it.
The transfer of Syria's chemical weapons arsenal was adopted as an alternative to international military intervention in the Syrian rebellion, and Kerry said the use of force was an option that remained on the table.
"Every indication we have is there is no legitimate reason that that is not happening now," said Kerry. "Therefore we call on (Syrian President) Bashar al-Assad to live up to his obligations or we will join together with our friends and talk about which, if any, of the options we deem necessary at this point to proceed forward."
Kerry spoke after the director of the mission said the Damascus regime needed to move more quickly.
Ahmet Uzumcu, director general of the Organization for the Prohibition of Chemical Weapons, said the Syrian government needs to establish a realistic schedule for the removal of the weapons and stick to it.
"While the two shipments [of chemicals] this month represent a start, the need for the process to pick up pace is obvious," Uzumcu said in a written statement issued Friday. "Ways and means must be found to establish continuity and predictability of shipments to assure ... that the program, while delayed, is not deferred."
Uzumcu's statement was in line with the allegation from the U.S. delegate to the OPCW, Robert Mikulak, that the international plan to dispose of Syria's chemical arms had "languished and stalled" with only 4 percent of the total arsenal of 530 metric tons of poison gas being removed.
Syria has contended it could not transport the weapons without additional equipment to protect against rebel attack and accused the United States of ginning up a crisis.
"We have adhered to the timetable," a spokesman said in remarks quoted by the Wall Street Journal. "There may be a few delays, but the OPCW are not unhappy. I think the Americans are trying to provoke an incident."
Mikulak had said in remarks issued by the U.S. State Department that Syria was stalling.
"These demands are without merit, and display a 'bargaining mentality' rather than a security mentality," Mikulak said, adding, "There should be no doubt that responsibility for the lack of progress and increasing costs rests solely with Syria."
Defense Secretary Chuck Hagel said in Warsaw, Poland, Thursday he made a personal appeal to his Russian counterpart to use Moscow's influence to bring the Assad regime back into compliance.
Russia is Syria's No. 1 diplomatic protector and is responsible with the United States for working out last year's deal with Syria to eliminate its chemical stockpile.
"We believe that this effort can continue to get back on track, even though we're behind schedule, but the Syrian government has to take responsibility for fulfilling its commitment that has been made," Hagel said in remarks quoted by the Washington Post.