WASHINGTON (AP) _ The Army has more than 1,000 leaking chemical weapons and the problem is likely to worsen in future years, service officials said Tuesday.

The leaking weapons are discovered by a complex series of sensors at the eight U.S. sites where they are stored, witnesses told the Senate Armed Services strategic weapons subcommittee.

''That's frightening, 1,000 leakers,'' said Sen. John Glenn, D-Ohio. ''That's a serious problem ... the problem is not going to get less'' as the weapons get even older.

Army Brig. Gen. David Nydam estimated the number of leaking weapons at ''more than 1,000,'' but added that the figure was only ''a small percentage'' of the total U.S. arsenal. He agreed with Glenn's assessment that the situation will worsen as the stockpile ages.

Nydam said the exact size of the U.S. chemical arsenal is classified. Published estimates have range from 25,000 to 40,000 tons, however.

When leaking weapons are discovered, they are enclosed in larger containers and then stored separately from the other weapons, Nydam said.

The weapons are stored in closed bunkers and are periodically checked to see if any are leaking, Nydam said.

Until recent months, the United States hadn't built any chemical weapons since 1969 and the Army's stockpile is now on average more than 25 years old. Unitary weapons include shells and bombs that are filled with a variety of nerve gases and chemicals.

As part of the Army's program of building new weapons, Congress ordered the service to come up with a safe method for destruction of the existing stockpile.

The Army has told Congress that it prefers to build closed incinerators at the eight U.S. sites because it is too dangerous to move the weapons.

The weapons are stored at the Aberdeen Proving Ground, Md.; Anniston Army Depot, Ala.; Lexington-Blue Grass Army Depot, Ky.; Newport Army Ammunition Plant, Ind.; Pine Bluff Arsenal, Ark.; Pueblo Army Depot, Colo.; Tooele Army Depot, Utah; and Umatilla Army Depot, Ore.

The largest stockpile, 42 percent of the total, is stored at Tooele. The list does not include U.S. weapons stationed in West Germany or stored on Johnston Atoll, a deserted island 400 miles south of Hawaii.

John Shannon, assistant secretary of the Army, told the subcommittee that the service is pushing ahead with plans to build the incineration plants, despite some strong local opposition.

Shannon said the criticism has come from communities around the Aberdeen, Newport and Lexington plants. The other five ''have expressed the desire that we get on with it,'' he said.

Sen. Dan Quayle, R-Ind., criticized the Army for its approach to swaying public opinion at the Newport site. ''There's been some progress, but we've got a long way to go,'' he said.

''We in the Senate become involved when our constituency feels it is short- changed,'' and that is the situation in Newport, Quayle said.

Shannon agreed, saying: ''We did not do a good job in Newport in the beginning, we'll have to do better.''

Shannon estimated the total cost of destruction at $2.7 billion and said the job will be completed by 1997, if the plants go ahead now.