U.N. Secretary-General Ban Ki-moon has urged haste.

"The precarious and unstable nature of the security situation further underlines the importance of expediting the removal of chemical weapons material from the Syrian Arab Republic as quickly and as safely as possible," Ban wrote last month in a letter to the U.N. Security Council obtained by the Associated Press.

Even among Western allies, the mission has aroused controversy. Originally, the materials were to be destroyed in Albania, but a public outcry there led the government to rescind its offer. No other country volunteered to host the operation, and the Organisation for the Prohibition of Chemical Weapons made the decision to destroy the materials at sea.

Still, Greece and Turkey have raised concerns, as have some officials in Italy.

The United States and others blame Assad for the Aug. 21 sarin attack that reportedly killed hundreds of civilians in the Damascus suburb of Ghouta. Assad has denied the accusation.

Under the threat of a U.S. military strike, Assad acknowledged maintaining a chemical arsenal and agreed to turn the stocks over to the international community.

By then, the Edgewood team had developed a deployable system for destroying the weapons. Pentagon leaders had seen a need for such a system in December 2012, after the first reports that Syria had used chemical weapons on opposition fighters, and gave the Edgewood specialists six months to get one ready.

The team expedited the project, delivering within months a system that ordinarily would have taken years to develop. The new Field Deployable Hydrolysis System was based on the technology used to destroy the U.S. stock of mustard agent at Aberdeen Proving Ground under the Chemical Weapons Convention of 1997.

Using the hydrolysis system, team members do not handle the materials directly. The chemicals are mixed in a closed container, and the resulting effluent is to be discharged into closed containers. Members are to wear masks with air hoses.

The team is expecting 540 tons of DF and 26 tons of mustard. The materials both are neutralized in the same way: They are mixed with water.

The resulting effluent is acidic. Team members plan to add chemicals to bring the pH level above neutral, creating a caustic liquid that some have likened to Drano. In that form, they say, it will be safer to store and transport to its eventual disposal site.

Harris stressed the experience of the specialists involved.

"Most of these people going have been doing this for 15, 20, maybe as long as 30 years," Harris said. He said the chemistry "has already been proven out in other elimination operations."

"We've done large-scale hydrolysis of both DF and mustard here in the United States," he said. "So we're using our experience, the procedures there, the lessons learned, and applying that to this mission as well."

For now, however, they wait. Since February, Harris said, teams of about a dozen have been rotating onto the Cape Ray for three weeks at a time to test the equipment and firm up procedures and plans.

Others remain back at Edgewood, where they are working on other projects while waiting for the call to deploy.

"You can imagine just the constant delays have put people's personal lives on hold," Harris said. "They can't really plan anything because they're waiting for this mission to occur."

Los Angeles Times reporter Patrick J. McDonnell and Reuters contributed to this article.