SEOUL, South Korea (AP) – A prominent South Korean scientist acknowledged Saturday that an unauthorized experiment to enrich uranium was conducted in three or four tests in early 2000, but said the amount in question was “so small it’s almost invisible.”

South Korea scrambled to deny it has ambitions for a nuclear program after the country admitted its scientists conducted an unauthorized experiment in 2000 to enrich a small amount of uranium. The revelation threatened to complicate an international standoff over communist North Korea’s nuclear weapons development.

The experiments were conducted between January and February 2000 at the government-affiliated Korea Atomic Energy Research Institute, its President Chang In-soon told The Associated Press Saturday.

“You often don’t get the desired result in the first test,” Chang said. “In the viewpoints of scientists, whether you had one test or 10 tests doesn’t make a big difference in this case.”

He said South Korean scientists enriched uranium to 10 percent during the tests – much lower than weapons grade, which requires enrichment of more than 90 percent.

Chang said the amount enriched was “so small it’s almost invisible.”

“It’s absurd for some people to speculate about weapons grade over this,” he said. “I don’t think any of the uranium was enriched to weapons grade.”

He said only 0.01 ounce of uranium was produced during the tests.

Several pounds of highly enriched uranium are needed to build a bomb, experts say.

South Korea on Friday called the experiment a “one-time” episode, saying the enrichment tests were terminated and never revived.

Seoul dismissed any comparisons between it and suspected nuclear programs in such countries as Iran and North Korea. It has insisted the enrichment tests will not derail U.S.-led efforts to dismantle rival North Korea’s nuclear programs.

Still such an experiment could provide the North with a pretext to further delay already stalled six-nation negotiations aimed at dismantling its nuclear facilities, which U.S. officials say are used to enrich uranium or yield plutonium for weapons.

The United States, the two Koreas, Japan, China and Russia have agreed to resume the talks by the end of the month, but no date has been announced.

The South Korean experiment was revealed to the International Atomic Energy Agency only last month. An IAEA inspection team wrapped up a weeklong inspection at the South Korean nuclear research center on Friday. It will report to the Vienna, Austria-based U.N. nuclear watchdog.

On Friday, Oh Joon, director general for international organizations at the South Korean Foreign Ministry, said different levels of enrichment took place during the 2000 experiment, but refused to say whether it produced any weapons-grade uranium.

The South Korean experiment took place two years before the United States confronted North Korea in October 2002 with a claim that the North was running a secret uranium enrichment program. North Korea denied it but angrily withdrew from the Nuclear Nonproliferation Treaty in early 2003, triggering a crisis.

North Korea says it is building a “nuclear deterrent” to counter what it calls plans by the United States and South Korea to unleash a nuclear war on the divided Korean Peninsula.

AP-ES-09-04-04 1423EDT