Western officials confirm to FOX News that there is intelligence suggesting that North Korean leader Kim Jong Il suffered a stroke on Aug. 14 and could be incapacitated — even wheelchair bound.

Sources tell FOX News that Assistant Secretary of State Christopher Hill's emergency visit to Beijing last week was more to talk about how to approach North Korea in the event of Kim's incapacitation, and less to talk about the reassembling of the Yongbyon nuclear facility.

A U.S. intelligence official told the Associated Press that there is reason to believe Kim is sick after he failed to show up at a North Korean national celebration on Tuesday. That official and another U.S. source spoke to the AP on condition of anonymity.

Kim has not been seen in public for a month and U.S. officials were closely watching Tuesday's military parade for signs to the leader's health or a shift in power.

North Koreans call Kim the "Dear Leader" and he holds absolute power in the Stalinist regime.

An official told FOX that one of the intelligence community's primary concerns is the line of succession in North Korea if, in fact, Kim is unable to rule or dies.

The line of succession is "opaque" and knowing the country's plan is difficult given how secretive its society remains. However, the offical told FOX that Kim Jong Il has family members and fellow politicians who could step in, but "there is no clear heir apparent."

Because of the reverence for the "Dear Leader," it is possible that he could "continue on" or linger on in a severely incapacitated state.

The centerpiece of Tuesday's celebration had been expected to be a massive military parade through Pyongyang's central Kim Il Sung Square — named after the communist country's founding figure — as normally happens in key anniversary years.

Kim attended the parade on the 50th and 55th anniversaries.

But Japan's Kyodo news agency and Russia's RIA-Novosti reported that the parade itself was toned down — lacking the usual massive displays of the army, navy and air force — and that Kim did not appear.

A spokesman for South Korea's main spy agency, the National Intelligence Service (NIS), said it could not immediately confirm Kim's absence, though said that the parade was found to have largely been conducted by civilian militia forces.

The rally involved about 1 million people, the NIS spokesman said, on condition of anonymity, citing office policy.

Kim's health has been a focus of intense interest because his fate is believed to be closely tied to that of the totalitarian state that he inherited in 1994 from his father in communism's first hereditary transfer of power.

Kim has been absent from public view since mid-August.

South Korean media have speculated that the 66-year-old Kim's health has worsened. South Korea's intelligence service has previously said Kim has chronic heart disease and diabetes — denied by Kim himself.

South Korea's Chosun Ilbo newspaper reported Tuesday that Kim collapsed on Aug. 22, citing an unnamed South Korean diplomat in Beijing. The diplomat got the information from a Chinese source, the paper said.

FOX News' Jennifer Griffin, FOX News' Catherine Herridge and the Associated Press contributed to this report.