While Al Qaeda remains the greatest threat to the U.S., Usama bin Laden is absent in controlling the terror network, CIA director Michael Hayden said Tuesday.

When asked why the U.S. had yet to capture the Al Qaeda leader, Hayden said he occasionally asks the CIA's head of counterterrorism the same question. His answer, he said, is that bin Laden is hiding.

"Please don't think I'm being flip with the answer," Hayden said at the Los Angeles World Affairs Council. "This man, who we really do want to kill or capture, is spending a great deal of his energy merely surviving and that's the next best state of nature as far as we're concerned. I'm serious."

Iran and North Korea both have the capability to produce nuclear weapons but Al Qaeda is the CIA's top nuclear concern because it is most likely to use them, Hayden said.

"There is no greater national security threat facing the United States than Al Qaeda and its associates," he said.

With regard to North Korea, a known nuclear power, and Iran, Hayden said: "The question is not of capability, but intent."

In 2006, North Korea conducted an underground nuclear test, removing any doubt it had the means to make a nuclear warhead.

Iran has not yet demonstrated a nuclear explosion, but Hayden said it has the scientific and industrial capacity to produce nuclear weapons "eventually." It fuels suspicion by refusing to allow international inspectors into its nuclear facilities.

"Tehran at a minimum is keeping open its option to develop nuclear weapons," Hayden said.

A U.S. intelligence assessment issued last year said Iran halted weapons design work in 2003, and that the nuclear weapons program had not resumed as of mid-2007. Hayden said intelligence still supports that conclusion.

Hayden's comments came the same day the International Atomic Energy Agency presented intelligence to 35 nations alleging Iran has plans to redesign a missile to accommodate a nuclear payload.

The Iranian representative to the organization says the information was fabricated. Gregory L. Schulte, the chief U.S. representative to the IAEA, said the evidence shows Iran has a weapons program.

In terms of the next White House administration, Hayden said the best way for the next president to help the CIA would be to "do nothing."

"If asked, I would offer my thoughts to the president-elect's team to pick people you trust who are competent to run these agencies, put them in those positions and the current structure will work well enough with good people ...," he said. "We're suffering reformation and transformation fatigue."

The Los Angeles World Affairs Council is a nonprofit organization that provides a forum for world figures to address its membership.

The Associated Press contributed to this report.