Iran is not close to having a nuclear weapon, which gives the United States and others time to try to persuade Tehran to abandon its suspected atomic arms program, U.S. Defense Secretary Robert Gates said on Sunday.

"They're not close to a stockpile, they're not close to a weapon at this point, and so there is some time," Gates said on NBC television's "Meet The Press."

Gates' comments followed a televised interview with Adm. Mike Mullen, head of the U.S. military Joint Chiefs of Staff, who told CNN's "State of the Union" that he believed Iran has enough fissile material to make a nuclear bomb.

"We think they do, quite frankly," Mullen said.

Mullen had been asked about a watchdog report issued by the International Atomic Energy Agency last month that said Iran had built up a stockpile of low-enriched uranium. The reported stockpile of 1,010 kg would be enough -- if converted into highly-enriched uranium -- to make a bomb, analysts have said.

The United States suspects Iran of trying to use its nuclear program to build an atomic bomb, but Tehran insists it is purely for the peaceful generation of electricity.

Gates said there has been "a continuing focus on how do you get the Iranians to walk away from a nuclear weapons program" in the Obama and Bush administrations.

U.S. President Barack Obama's administration favors diplomatic engagement with Tehran to defuse the dispute over its nuclear intentions, but has called Iran's nuclear program an "urgent problem" the international community must address.

The challenge, Gates said, is finding a balance between sanctions to pressure Iran and incentives for engagement with the United States and Europe. A sharp decline in oil prices since last year increases the chances for a resolution. "There are economic costs to this program; they (the Iranians) do face economic challenges at home."

MULLEN TALKS OF 'VERY BAD OUTCOME'

U.S. spy agencies believe Iran lacks enough weapons-grade uranium to make a bomb, but cannot rule it out, Adm. Dennis Blair, the U.S. director of national intelligence, told Congress last month.

"Iran probably has imported at least some weapons-usable fissile material but (we) still judge it has not obtained enough for a nuclear weapon," he said. "We cannot rule out that Iran has acquired from abroad or will acquire in the future a nuclear weapon or enough fissile material for a weapon."

He reiterated a view that Iran was undertaking two of three activities needed for a nuclear arms program -- developing uranium-enrichment technology and nuclear-capable ballistic missile systems. U.S. intelligence agencies have said Iran suspended developing a nuclear warhead, the third activity.

"Iran having nuclear weapons, I've believed for a long time, is a very very bad outcome -- for the region and for the world," Mullen said.

CIA Director Leon Panetta last week declined to discuss any possible new U.S. policies being considered in this area, saying this is classified.