Aiming his words at Democrats in congress, Bush said: "I guess my reaction to all the noise about, you know, 'he wants to go to war,' is, first of all I don't understand the tactics, and I guess I would say it's political."
The president said he had "a comprehensive policy aimed to solve this peacefully" and vowed to "press hard" for Iran to freeze sensitive nuclear work that could be a key step towards an atomic arsenal.
Bush said: "We're working towards that end, and we're pressuring the regime through diplomatic channels, ie, a Chapter Seven resolution at the United Nations, thereby making Iran one of the few nations under Chapter Seven.
"Iranian people are good, decent, honourable people. And they've got a government that is belligerent, loud, noisy, threatening, a government which is in defiance of the rest of the world and says, we want a nuclear weapon.
"And so our objective is to continue to keep the pressure in hopes that rational folks will show up and say, it's not worth it, it's not worth the isolation."
Tehran has repeatedly denied Washington's allegations that its nuclear programme hides a quest for an atomic bomb and has rejected US charges of smuggling bombs to Iraqi fighters who target US troops as "without foundation."
The White House, its credibility badly damaged by the flawed case for invading Iraq, vouched for charges that Iranians had been arming Iraqis with deadly bombs with the knowledge of the government in Tehran.
Asked to give proof that Iran knew about the bomb shipments, Tony Snow, White House spokesman, said: "Let me put it this way: There's not a whole lot of freelancing in the Iranian government, especially when it comes to something like that.
"To counter that position, you would have to assume that people were able of putting together sophisticated weaponry, moving it across a border into a theatre of war and doing so unbeknownst and unbidden."