WASHINGTON - Even as the international effort to destroy Syria's vast chemical weapons stockpile lags behind schedule, a similar U.S.-backed campaign carried out under a cloak of secrecy ended successfully last week in another strife-torn country, Libya.

The United States and Libya in the past three months have discreetly destroyed what both sides say were the last remnants of Moammar ­Gadhafi's lethal arsenal of chemical arms. They used a transportable oven technology to destroy hundreds of bombs and artillery rounds filled with deadly mustard agent, which U.S. officials had feared could fall into the hands of terrorists. The effort also helped inspire the use of the technology in the much bigger disposal plan in Syria.

Since November, Libyan contractors trained in Germany and Sweden have worked in bulky hazmat suits at a tightly guarded site in a remote corner of the Libyan desert, 400 miles southeast of Tripoli, racing to destroy the weapons in a region where extremists linked to Al-Qaida are gaining greater influence. The last artillery shell was destroyed on Jan. 26, officials said.

As Libya's weak central government grapples with turmoil and unrest, and as kidnappings and assassinations of military and police officers accelerate in the country's east, U.S. and international weapons specialists hailed the destruction of the Libyan stockpile as a bright spot in an otherwise gloomy security environment.

"It's a big breakthrough," said Paul F. Walker, an arms control expert with the environmental group Green Cross International who has helped in efforts to demilitarize the U.S. and Russian chemical ­weapons stockpiles since the 1990s. "Even though Libya's chemical stockpile was relatively small, the effort to destroy it was very difficult because of weather, geography and because it's a dangerous area with warring tribes, increasing the risks of theft and diversion," he said.

Model for Syria

Libya's last 2 tons of chemical weapons were dwarfed by the 1,300 tons Syria has agreed to destroy. But U.S. and international arms experts say the need for easily transportable and efficient technology to wipe out the Libyan arms became a model for the Syria program underway.

These chemical containers were in an unguarded storage facility in the Libyan desert, some 62 miles south of Sirte, when civil war broke out in 2011. U.S. officials were concerned then about preventing the proliferation of chemical weapons.

For Libya's fragile transitional government, such collaboration with the West on security matters is a delicate issue. It gives the country's leaders desperately needed assistance to defuse internal threats, but also risks accusations of compromising national sovereignty.

On Sunday, the White House said it would ensure that the Syrian government complied with an accord to give up its chemical arsenal despite missed deadlines and delays in carrying out the deal.

The White House chief of staff, Denis McDonough, said on the CBS News program "Face the Nation" that the deal was "not falling apart, but we would like to see it proceed much more quickly than it is."

Gadhafi chapter closed

The disposal of the last of Libya's chemical weapons closes a chapter that Gadhafi began in early 2004, when his government turned over a vast cache of nuclear technology and chemical stockpiles to the United States, Britain and international nuclear ­inspectors.

At that time, Libya declared for destruction 24.7 metric tons of sulfur mustard that when loaded into bombs or artillery shells and exploded creates a toxic mist that penetrates clothing, burns and blisters exposed skin, and can kill with large doses or if left untreated.

Libya had destroyed about half these stocks when civil war broke out in 2011. The ­majority of Libya's mustard agents were stored then in large, bulky ­containers.