The US Defense Department said in a statement it will not to able to liquidate 45 percent of its chemical stockpile by April 29, 2004, as required by the 1997 Chemical Weapons Convention.
"The United States is therefore requesting the Organization for the Prohibition of Chemical Weapons (OPCW) grant an extension of the 45 percent destruction deadline," the statement said.
The military is now expected to reach the elusive milestone by December 2007, the Pentagon said.
No detailed explanation for the postponement was given. But the department pointed out that its chemical demilitarization program "has had several delays due to unresolved political and operational issues that forced operational shutdowns or postponed start-up dates."
All told, only about 23 percent of the US chemical stockpile have been destroyed thus far, the Pentagon admitted.
The Chemical Weapons Convention, which has been signed by more than 150 countries, bans production, acquisition, stockpiling, transfer and use of chemical weapons -- and compels its signatories to get rid of their arsenals by 2007.
At the time of the signing, the United States admitting having about 31,000 tonnes of such weapons, including 3.3 million bombs, rockets, artillery shells and cartridges and 315,682 binary munitions, in which chemicals are mixed in flight to produce deadly gas.
To ensure their destruction, the US Army is managing a network of incinerators and other disposal facilities, including the plants at Johnston Atoll in the Pacific Ocean and near the town of Tooele in the western state of Utah.
More disposal facilities are operating in Maryland, Alabama, Kentucky, Indiana, Arkansas, Colorado and Oregon.
But defense officials have complained that the Tooele incinerator has stood idle for eight months due to an investigation of safety practices following an incident where a worker was exposed to a small amount of chemical agent during a maintenance operation.
Weapons destruction at Pueblo, Colorado, and Blue Grass, Kentucky, has been slow due to engineering and managerial problems, according to disarmament experts.
And the Army incinerator in Anniston, Alabama, was able to begin operating only last month due to technical delays and legal challenges raised by local residents concerned that an accident or a leak of chemical agents could have devastating consequences for the rural community.
According to disarmament experts, the program has been also plagued by serious cost overruns and miscalculations. Projections made in the mid-1980s held that the whole arsenal could be destroyed for only 1.5 billion dollars. Current estimates put the overall cost at about 20 billion.
As a result, the convention's final 2007 deadline is also likely to slip, say specialists inside and outside the government.
The Pentagon made it plain by saying that "the United States will address the extension of the 100 percent deadline at a later date, as allowed under the convention."
It assured, however, that Washington fully intended to honor all of its commitments under the accord.