Up to 30 percent of the bomb fuses possessed by South Korea's air force may be useless because they are too old, military sources said.

"The current fuses inventory, mostly comprising the mechanical M-904/905 units, is too old to use," a military officer told The Korea Times. "They are 10-20 years past their due shelf life date," the officer said on condition of anonymity.

The officer's remarks were backed up by two air force officers. They estimated, from their experience during training practices, that 20-30 percent of fuses fail to detonate, the Times' report said.

However, South Korea's army fares better because it has regular inspection of its munitions, unlike the air force. The air force buys its fuses and aircraft bombs from the United States through the foreign military sales program but that doesn't include inspection services in later life, the newspaper said.

"It's difficult to dispose of or replace the older fuses," an official at South Korea's Joint Chiefs of Staff said. "We're not sure the equipment is working 100 percent but we believe they're still usable."

The South Korean air force has more than 10,000 bombs, the article said. This includes the MK-82, a low-drag general-purpose unguided bomb weighing around 500 pounds and the BLU-109 penetration bomb, nominally weighing around 535 pounds.

In 1985, Lockheed Missile and Space Corp. received a contract with the U.S. Air Force to develop a hard-target weapon to smash through concrete shelters and other hardened structures before exploding. The BLU-109/B -- bomb live unit -- with its delayed-action fuse entered service in the United States in 1985.

The Korea Times article said the South Korean air force has about 1,200 precision-guided Joint Direct Attack Munition bombs.

JDAMs are kit conversions to make unguided bombs, or dumb bombs, into all-weather smart munitions. These are meant for the air force's McDonnell Douglas/Boeing KF-15E Strike Eagle aircraft and the General Dynamics and Lockheed Martin F-16 Fighting Falcon planes.

Most of the JDAMs are equipped with newer electrical fuses, such as the FMU-139/152, the article said.

Conversion of the air force's dumb bombs, as well as inspecting fuses, has been postponed over the years because of financial constraints. "It's a budget issue," a retired air force brigadier general told the Times.

"The military has a comprehensive package of arms improvement programs and fuse procurement has been postponed inevitably despite its importance. In the mid- to long-term, of course, we should consider upgrading fuse technology."

More money could be forthcoming in future budgets, he said. "We don't want to have newer fighter aircraft with obsolete bombs."