US President George W. Bush said Monday that force is not necessarily required to stop Iran from having a nuclear weapon, and he dismissed reports of plans for a military attack against Tehran as "wild speculation." Bush said his goal is to keep the Iranians from having the capability or the knowledge to have a nuclear weapon. "I know we're here in Washington (where) prevention means force," Bush said. "It doesn't mean force necessarily. In this case it means diplomacy." Bush and other administration officials have said repeatedly that the military option is on the table, and White House officials acknowledge "normal" military planning is under way. Several reports published over the weekend said the administration was studying options for military strikes, and an account in The New Yorker magazine raised the possibility of using nuclear bombs against Iran's underground nuclear sites. Bush did not directly respond to that report but said, "What you're reading is just wild speculation." But Bush said he was correct to include Iran in the "axis of evil" with Iraq and North Korea and he's glad to see other countries taking the threat from Iran seriously, too. "I got out a little early on the issue by saying axis of evil," Bush said. "But I meant it. I saw it as a problem. And now many others have come to the conclusion that the Iranians should not have a nuclear weapon." The White House sought Monday to minimize new speculation about a possible military strike against Iran while acknowledging that the Pentagon is developing contingency plans to deal with Tehran's nuclear ambitions. The Pentagon has refused to further describe its planning. White House press secretary Scott McClellan refused to confirm or deny a report in The New Yorker magazine that raised the possibility of using nuclear bombs against Iran's underground nuclear sites. "Those who are seeking to draw broad conclusions based on normal military contingency planning are misinformed or not knowledgeable about the administration's thinking," he said. British Foreign Secretary Jack Straw, in an interview with the British Broadcasting Corp. on Sunday, called the idea of a nuclear strike "completely nuts." Straw said Britain would not launch a pre-emptive strike on Iran and he was as "certain as he could be" that neither would the US. He said he has a high suspicion that Iran is developing a civil nuclear capability that in turn could be used for nuclear weapons, but there is "no smoking gun" to prove it and rationalize abandoning the plodding diplomatic process. "The reason why we're opposed to military action is because it's an infinitely worse option and there's no justification for it," Straw said. Defense experts say a military strike on Iran would be risky and complicated. US forces already are preoccupied with Iraq and Afghanistan, and an attack against Iran could inflame US problems in the Muslim world. The UN Security Council has demanded Iran suspend its uranium enrichment program. But Iran has so far refused to halt its nuclear activity, saying the small-scale enrichment project was strictly for research and not for development of nuclear weapons. Bush has said Iran may pose the greatest challenge to the United States of any other country in the world. And while he has stressed that diplomacy is always preferable, he has defended his administration's strike-first policy against terrorists and other enemies.