According to prepared remarks for delivery at an international defense conference, Rumsfeld said the U.S. stands "with the Iranian people, who want a peaceful, democratic future."
"The Iranian regime is today the world's leading state sponsor of terrorism," he said. "The world does not want, and must work together to prevent, a nuclear Iran."
Meanwhile, In Vienna, Austria, the International Atomic Energy Agency declared that Iran's breaches of the nuclear nonproliferation treaty and a lack of confidence that it is not trying to make weapons are linked to a decision to ask for Tehran's referral to the U.N. Security Council, according to a draft resolution made available Saturday to The Associated Press.
The resolution submitted to the 35-nation board of the IAEA expresses "serious concerns about Iran's nuclear program." It recalls "Iran's many failures and breaches of its obligations" to the nonproliferation treaty. And it expresses "the absence of confidence that Iran's nuclear program is exclusively for peaceful purposes."
Rumsfeld painted a stark picture of a lengthy war against terrorism that lies ahead, appealing to allies to show unity and increase military spending to defeat the threat of a "global extremist Islamic empire."
Rumsfeld said terrorists hope to use Iraq as the "central front" in their war, turning it into a training and recruitment area like they had done in Afghanistan under the Taliban. He warned "a war has been declared on all of our nations" and said their "futures depend on determination and unity in the face of the terrorist threat."
"We could choose to pretend, as some suggest, that the enemy is not at our doorstep. We could choose to believe, as some contend, that the threat is exaggerated.
"But those who would follow such a course must ask: what if they are wrong? What if at this moment, the enemy is counting on being underestimated, counting on being dismissed, and counting on our preoccupation," Rumsfeld said.
On Friday, Iran said it no longer would consider aenrichment program to Russia if it is referred to the U.N. Security Council over suspicions it might be seeking nuclear weapons.
If Iran's nuclear file goes to the Security Council, "there will be no way we can continue with the Russian proposal," said Javad Vaeidi, deputy head of the powerful National Security Council and a top nuclear negotiator.
Rumsfeld was to follow German Chancellor Angela Merkel in the opening speeches on the second day of 42nd annual Munich security conference, a prestigious gathering in southern Germany, which defense experts and policy-makers traditionally use for frank exchanges.
The conference is focused on the trans-Atlantic relationship between the U.S. and Europe.
Rumsfeld said violent extremism is a danger faced as much in Europe as in the United States.
"The struggle ahead promises to be a long war that will cause us all to recalibrate our strategies, perhaps further adjust our institutions, and certainly work closely together," he said.
He said Islamic militants are on the move and have to be checked.
"They seek to take over governments from North Africa to Southeast Asia and to re-establish a caliphate they hope, one day, will include every continent," he said. "They have designed and distributed a map where national borders are erased and replaced by a global extremist Islamic empire."