GENEVA, (Reuters) - North and South Korean diplomats clashed angrily at a United Nations disarmament meeting on Thursday, with North Korea accusing The United States of developing an offensive nuclear weapons system.

The closing session of the U.N. Conference on Disarmamment was dominated by a clash between the delegations of North and South Korea, who traded accusations of military provocation on their divided peninsula.

North Korean ambassador Ri Tcheul angrily denounced a "U.S. armada" heading for the region following a naval skirmish in the Yellow Sea last week between South and North Korean navy boats, the first since their 1950-53 war.

"The Democratic People's Republic of Korea, desiring peace and security, is prepared to have anyone touching its territory pay a very high price," Ri told the 61-member state body.

"Since we are under constant threat of nuclear weapons, the Democratic People's Republic of Korea backs the principle that all nuclear arms must be destroyed as soon as possible," he said.

North Korea's envoy attacked a U.S. plan, backed by Japan, to develop an ambitious national missile defence system. The scheme would be land-based, but probably use space sensors to provide early warning of enemy or accidental launches.

"The country with the largest nuclear arsenal in the world, with powerful military forces, and another, the first victim of the nuclear war, are jointly developing this dreadful action.

"It is nothing other than an offensive weapon system designed to maintain military supremacy..." Ri said.

South Korea's delegate accused North Korea of "continuous intrusions," but said his country was determined to pursue its policy of engagement with Pyongyang.

U.S. ambassador Robert Grey took the floor briefly at the conference to support "my Korean ally" in Seoul.

The United Nations disarmament body ended its second session of 1999 with dim prospects of launching negotiations on nuclear fissile material at its final session starting in July, diplomats said.

Earlier, India's envoy expressed frustration at the six-month impasse at the Geneva arms forum. "We express our deep disappointment at the current situation," envoy Savitri Kunadi said in a speech.

"The current impasse in efforts for the CD's programme of work are related to the inflexible positions of a few delegations that have prevented agreement being reached on the two outstanding issues -- nuclear disarmament and outer space."

Diplomats said she was referring to the three Western nuclear powers -- the United States, Britain and France.

The three have refused to launch negotiations aimed at total elimination of nuclear weapons, arguing that arsenals are being cut under U.S.-Russian pacts. The United States is the only member opposed to setting up a CD committee on outer space.

The CD holds its final session from July 26-September 8.

"Prospects are very dim for a breakthrough. This year is a write-off," said a western diplomat.