President Bush, preparing for this week's much-anticipated campaign debate on foreign policy, is insisting Iran will not develop a nuclear weapon.

"My hope is that we can solve this diplomatically," Bush said in a TV interview broadcast Monday. "We are working our hearts out so that they don't develop a nuclear weapon, and the best way to do so is to continue to keep international pressure on them."

Pressed on whether he would allow Iran to build a bomb, Bush said: "No, we've made it clear, our position is that they won't have a nuclear weapon."

Bush's comments on FOX News Channel's "The O'Reilly Factor" did not mark new policy. In June 2003, Bush said that "the international community must come together to make it very clear to Iran that we will not tolerate the construction of a nuclear weapon."

But Bush has not spoken out so forcefully on the matter since signs emerged recently that Iran could be on the path toward developing a bomb.

Iran defied rules set by 35 nations and announced it had started converting raw uranium into the gas needed for enrichment, a process that can be used to make nuclear weapons. While insisting its intentions are peaceful, Iran pledged to continue even if it means a rupture with U.N. monitors and an end to inspections of its nuclear facilities.

Thursday's presidential debate centers on foreign policy, and Iran is likely to come up. Bush and his Democratic challenger, Sen. John Kerry (search), have modest differences on how to confront the issue.

Kerry charges that Bush's Iraq policies "took our attention and our resources away" from dealing with Iran.

Kerry holds out some hope that a negotiated solution with Iran is possible. He said the United States and other nations should "call their bluff" by offering nuclear fuel for peaceful purposes, then taking back the spent fuel so it can't be used for weapons.

If that process fails, the United States could try to ensure that the International Atomic Energy Agency takes the issue to the U.N. Security Council (search), where Iran could face sanctions.

In 2001, Bush called Iran part of an "axis of evil," along with Iraq and North Korea. Yet, he too favors diplomacy, though his administration has been divided on how to deal with it. Some, mostly in the Pentagon, favor a tougher approach. Others, mostly in the State Department, believe some accommodation is possible with Iranian moderates.

Bush is putting the finishing touches on his debate preparation this week.

He is done sparring with mock-debate partner Sen. Judd Gregg (search), R-N.H., said White House communications director Dan Bartlett.

Bush planned a low-profile day at his Crawford, Texas, ranch Tuesday, "crystallizing" his thoughts on policy and sharpening zingers, Bartlett said.

The ranch has an important mind-clearing effect, he said.

"I'm sure some of the best zingers he's given have been (written) out there with a fishing pole in his hands," Bartlett said.