Sept. 19 (Bloomberg) -- Defense Secretary Robert Gates said the U.S. is monitoring North Korea closely for potential instability in the communist nation following reports leader Kim Jong Il suffered a stroke last month.

``At this point it's not entirely clear how seriously ill he is,'' Gates told reporters yesterday in London, where he is holding informal talks with NATO counterparts. The U.S. and ``all of North Korea's neighbors are concerned about instability, in no small part because of the possibility of large flows of refugees.''

Kim, who has led the impoverished nation of 23 million people since his father Kim Il Sung died in 1994, failed to attend 60th anniversary celebrations of North Korea's founding on Sept. 9, fueling speculation about his health.

A U.S. intelligence official, who declined to be identified, said earlier this month the communist leader may have suffered a stroke in recent weeks. North Korean officials deny their 66-year-old leader is sick.

Gates said he foresaw no repercussions for U.S. troop commitments in Iraq and Afghanistan if a conflict erupts between South Korea and North Korea.

The neighbors are still technically at war after their 1950-53 conflict ended without a peace agreement. There are 28,500 U.S. soldiers stationed in South Korea.

``If there ever should be a conflict, the main American contribution is not ground forces,'' said Gates. ``So the connection with Afghanistan and Iraq, I think, is irrelevant.''

It will take three to five months to ascertain how stable Kim's condition is, a South Korean government official, who declined to be identified because of the sensitivity of the issue, said last week.

His grip on power may be weakened by ill health and the regime will go through a period of ``transition'' as he recovers, the official said.

South Korea has received some intelligence that Kim is recovering, Unification Ministry spokesman Kim Ho Nyoun said last week.

To contact the reporter on this story: Ed Johnson in Sydney at ejohnson28@bloomberg.net.

Last Updated: September 18, 2008 21:10 EDT