U.S. Defense Secretary Donald Rumsfeld says he does not see North Korea as an immediate military threat to South Korea.

Rumsfeld said during a visit Sunday to a U.S. military base in Alaska that the North's biggest threat is selling weapons to other nations or to terrorists.

The United States, South Korea, and several other Asian nations, China, Japan, Russia have so far not been able to persuade North Korea to give up its nuclear program, which Washington believes is aimed at building nuclear weapons.

Donald Rumsfeld (l) with Russia's Defense Minister Sergei Ivanov in Fairbanks, Alaska

Later, Rumsfeld said the Pentagon is considering replacing the nuclear warheads on a number of intercontinental ballistic missiles with conventional weapons if a preemptive strike against terrorists is needed.

Russian Defense Minister Sergei Ivanov, who met with Rumsfeld Sunday in Alaska, said the Kremlin is not yet ready to embrace the idea and said such a missile launch could be mistaken for a nuclear attack

He said there are different solutions for a preemptive strike against terror groups, but added that his government is ready to discuss the matter with U.S. officials.

Rumsfeld Sunday also toured a silo at Alaska's Fort Greely, where another missile interceptor is expected to be installed this week.

The system is is built to shoot rockets at enemy missiles headed to the United States. Rumsfeld said he will not declare that the nearly $100-billion system would work until he sees more extensive tests.

Some information for this report was provided by AFP, AP and Reuters.