The comments, delivered by the U.S. representative to the international chemical weapons watchdog, marked some of the strongest public criticism of Syria's commitment to relinquish its chemical stockpile.
Syria agreed to surrender its arsenal after a deadly chemical attack in August on a rebel-held suburb of Damascus raised the threat of punitive U.S. missile strikes. President Barack Obama has touted the agreement as a victory and a major policy achievement for his administration on Syria's intractable civil war.
The Organization for the Prohibition of Chemical Weapons is leading the mission to eliminate Syria's 1,300-metric ton stockpile by a June 30 deadline.
Under the OPCW's tight timeline, the most toxic chemicals in Syria's arsenal were to have been removed from the country by Dec. 31, but that deadline was missed due to poor security amid Syria's raging civil war as well as other factors. So far, just two small consignments of chemicals have been shipped out.
"The effort to remove chemical agent and key precursor chemicals from Syria has seriously languished and stalled," Robert Mikulak told the OPCW's 41-nation executive council in a closed-door meeting. His remarks were later posted on the State Department's website.
Mikulak, who is the U.S. representative to the OPCW, acknowledged that the timeline for the removal of Syria's most dangerous chemicals was ambitious, but he expressed frustration that a month after the deadline "only 4 percent" of the chemicals has been removed "and the Syrian government will not commit to a specific schedule for removal."
He called on Damascus to comply with the U.N. resolution for Syria to relinquish its chemical stockpile.
According to the OPCW timeline, all but 100 tons of chemicals are to be removed by Feb. 5 — a deadline that surely will not be met.
Mikulak said Damascus has cited security concerns for the delay in transporting the chemicals to the port city of Latakia for destruction abroad. But he dismissed Syria's insistence on receiving additional security equipment, such as armored jackets for shipping containers and high-tech electronics, to secure the convoys, saying the demands were "without merit."
"Syria's requests for equipment and open-ended delaying of the removal operation could ultimately jeopardize the carefully timed and coordinated multi-state removal and destruction effort," he added. "For our part, the international community is ready to go."
An American ship, the MV Cape Ray, is on its way to the Mediterranean Sea to pick up the most toxic chemicals in Syria's stockpile, including mustard gas and raw materials for making sarin nerve agent. The Cape Ray is equipped with two machines that will render the chemicals them inert.
Danish and Norwegian cargo ships are picking up the chemicals from Latakia and will transfer them to the Cape Ray in the Italian port of Gioia Tauro.
"There should be no doubt that responsibility for the lack of progress and increasing costs rests solely with Syria," Mikulak said.
The Syrian government had no immediate comment.
The mission to rid Syria of its chemical arsenal is one layer in the country's exceedingly complex and bloody civil war. The conflict, which began in March 2011 as largely peaceful protests before shifting into an armed insurgency, has killed more than 130,000 people, forced 2.3 million to seek refuge abroad and unleashed a devastating humanitarian crisis at home and across the region.
On Thursday, the United Nations delivered hundreds of relief parcels to a besieged rebel-held Palestinian neighborhood in the Syrian capital that has suffered from crippling shortages of food and medicine for months.
The Yarmouk camp, located on the southern edge of Damascus, is one of the hardest-hit of a number of opposition enclaves under tight blockades imposed by pro-government forces. Activists said Wednesday that at least 85 people had died in Yarmouk since mid-2013 as a result of starvation and illnesses exacerbated by hunger or lack of medical aid.
Chris Gunness, a spokesman for the U.N.'s UNRWA agency that supports Palestinian refugees, said a convoy carrying 900 food parcels entered Yarmouk on Thursday morning. He added that despite "chaotic scenes," by noon 720 parcels had been distributed.
"We are encouraged by the delivery of this aid and the cooperation of the parties on the ground," Gunness said, adding that 18,000 Palestinians, including women and children, were in need of assistance.
Anwar Raja, a Palestinian official in Syria, said a number of elderly people also were to be evacuated from Yarmouk.
In the nearby suburb of Daraya, meanwhile, Syrian army helicopters dropped barrels packed with explosives and fuel, killing at least 11 people, the Britain-based Syrian Observatory for Human Rights said.
In a new report released Thursday, Human Rights Watch accused the government of using controlled explosions and bulldozers to raze thousands of residential buildings, in some cases entire neighborhoods, in a campaign that appeared designed to punish civilians sympathetic to the opposition or to cause disproportionate harm to them.
The demolitions took place between July 2012 and July 2013 in seven pro-opposition districts in and around the capital, Damascus, and the central city of Hama, according to a 38-page report by Human Rights Watch. The New York-based group said the deliberate destruction violated international law, and called for an immediate end to the practice.
The report includes satellite images of the neighborhoods before and after the demolitions, providing a window on the scale of the destruction.
Buildings in the Hama neighborhood of Masha al-Arbaeen, a wedge-shaped district bordered by highways on three sides, are clearly visible in a photo dated Sept. 28, 2012. In a second photo from Oct. 13, the buildings have been pulverized into a white smudge, while the adjacent neighborhoods remain untouched.
The government also has been accused of using airstrikes and rocket attacks indiscriminately against residential areas.
In a video from last week, men frantically dug through rubble after an alleged airstrike in Aleppo and unearthed a toddler, still alive and with her face covered in dust. The rescuers chanted "God is greatest" as they pulled Ghina Khalil from the smashed building. The video — http://www.youtube.com/watch?v=lckNgtlLQ6I — corresponded with Associated Press reporting of the events depicted.
Associated Press writers Mike Corder in The Hague, Netherlands, Albert Aji in Damascus, Syria, and Bassem Mroue and Yasmine Saker in Beirut contributed to this report.