The official, Sigrid Kaag, said nothing about attacks on Syrian storage facilities. But she said that “security is a big factor in all that takes place” and that the mid-2014 deadline for the complete destruction of the Syrian arsenal could still be met despite the civil war raging in Syria.

Image Crew members of a Danish commercial vessel in the Syrian port of Latakia on Jan 5.



Credit Petros Karadjias/Associated Press

Ms. Kaag said the public should not worry about the deadliest compounds, known as Priority 1 chemicals, aboard the Danish vessel, which will remain at sea with the cargo, then dock at Latakia again to collect the remainder when it is ready to be loaded.

Once the entire stockpile of the deadliest compounds, estimated to total 500 tons, is on the ship, it will go to Italy, where the chemicals will be transferred to an American naval vessel equipped to render them harmless.

“They’re safe and secure, they’re properly guarded, and all efforts have been made to keep them in that way,” Ms. Kaag told reporters. “Everything has been done to make sure that this is properly handled.”

She declined to specify how many tons were in the initial cargo, how long the Danish ship would wait offshore or how many times it would have to return to Latakia to load the remainder. Such details, she said, are part of a “very tightly held, and I think rightly so, operation.”

Asked to rate the level of cooperation from the Syrian authorities, Ms. Kaag described it as constructive, but said “I’m not in the rating business.”

The transportation and export of the most dangerous chemicals, which include mustard gas, VX nerve agent and the agents needed to create sarin gas, have always been considered the most hazardous steps of the operation. Yet an unusually collaborative international effort is underway, including maritime security provided by Russia, China, Norway and Denmark.

Syria’s pledge to renounce chemical weapons and join the treaty that bans them was a product of intensive diplomacy by the United States and Russia. The agreement averted an American military response to a chemical weapons attack outside Damascus on Aug. 21 that killed hundreds of civilians. The United States blamed the government of President Bashar al-Assad; Mr. Assad and rebels seeking to depose him blamed each other.