(CBS) International efforts to destroy chemical weapons are far behind schedule, raising proliferation risks, a congressional report finds.

The General Accounting Office reported Tuesday that both Russia and the United States — which account for 95 percent of declared weapons stockpiles — will miss the deadline for destroying their arsenals under the Chemical Weapons Convention, or CWC.

"The CWC's nonproliferation goals have proven more difficult to achieve than originally anticipated," GAO reported.

The 1997 chemical weapons treaty — which "bans the production, possession, and use of chemical weapons" — envisioned member countries destroying their chemical weapons by 2007, or by an extended deadline of 2012. The targeted weapons include sarin and VX nerve gas, and mustard agent.

But according to GAO, the United States so far has destroyed only about 24 percent of its 27,000 metric tons of chemical weapons, and is not projected to get rid of the rest until 2014, two years after deadline.

Russia has destroyed a mere 1.1 percent of its 40,000 metric ton-stockpile, and will not complete its obligations until 2027.

"Without a credible plan, Russian destruction efforts may experience further delays, leaving the Russian chemical weapons stockpile vulnerable to theft or diversion," the report noted.

In comments to the GAO, the State Department said Tuesday's report "tarnishes the bright success" of the chemical weapons treaty. But worldwide, only 11 percent of the 70,000 metric tons of declared chemical weapons stockpiles have been destroyed.

"Member states are experiencing delays in destroying their chemical weapons stockpiles, adopting comprehensive national laws to criminalize the possession and use of chemical weapons, and submitting timely and accurate declarations of their CWC-related activities," the GAO found.

To date, 161 countries have joined the chemical weapons treaty, but fewer than 40 percent of them have passed laws banning chemical weapons activities. And in 2001, the State Department said China, Iran, Russia and Sudan had not revealed the full scope of their stockpiles to the world.

The United States is running three sites for destroying chemical weapons and will have three more on-line soon, but in September, the Pentagon announced it would miss an April 29 deadline to destroy 45 percent of its stockpile. The United States was granted an extension until December 2007.

According to an earlier GAO report, Congress told the Pentagon in 1986 to destroy lethal chemical agents.

But "persistent delays have occurred due to plant safety issues, environmental requirements, and funding shortfalls," GAO said this week.

Almost half of the declared U.S. stockpile is at a facility in Toole, Utah, where nerve and blister agent are held.

Blister and nerve agent are also found at Johnston Atoll; Anniston, Ala.; Umatilla, Ore.; Blue Grass, Ky.; and Pine Bluff, Ark.

A site at Newport, Ind., has only nerve agent, while two sites — Aberdeen, Md. and Pueblo, Colo. — have only blister agent.

International donors have given Russia $585 million to destroy its stockpiles, and committed about a billion dollars more.

From 2001 to 2003, Moscow budgeted about $420 million for the project, but spent only $95 million. Its sole destruction facility took 11 years to build.

The GAO says options for speeding Russia's destruction of chemical weapons include increased funding to build new disposal facilities, or conditioning other aid to Russia on Moscow's improved compliance with the CWC.

Money might also be directed toward improving security at sites where the Russian stockpile is stored.