"Let's leave military options aside, we have already seen that they don't amount to anything," Schröder said during an electoral meeting in the northern city of Hanover.

The chancellor's statement followed an interview aired Friday on Israeli public television in which US President George W. Bush said that "all options are on the table" when asked if the use of force was an alternative to faltering diplomacy with Iran.

In an interview to be published Sunday in the German weekly Bild am Sonntag, Schröder said he considered any military option "extremely dangerous."

"This is why I can with certainty exclude any participation by the German government under my direction," he said.

Schröder "very concerned"

The Social Democrat chancellor -- who in polls leading up to early legislative elections on September 18 is lagging behind his Christian Democrat challenger Angela Merkel -- added that he was "very concerned" by the situation in Iran.

Tehran must not be allowed to manufacture nuclear weapons, he said, adding that numerous European propositions had been made "in order to induce Iran to change its position."

Schröder vehemently opposed the US-led invasion of Iraq in 2003, and has since opted to train Iraqi security forces in the United Arab Emirates rather than deploying German troops to the battle zone.

"Military operations always introduce the risk of unmanageable escalation," German Foreign Minister Joschka Fischer said on the sidelines of an electoral meeting Saturday in Schwerin. "We must again place our bets on diplomatic means," he added.

Friedbert Pflüger, a spokesman for the opposition Christian Union parties, criticised Schröder in an interview to appear Sunday in the newspaper Welt am Sonntag, saying that he "must not try to campaign on this issue."

Schröder's criticism of the looming Iraq war during the 2002 election campaign was widely seen as key to his re-election.

Escalating situation

Iran broke the seal on its uranium conversion facilities in Isfahan on Wednesday under the auspices of recommencing its nuclear energy program.

Suspicious of Iran's 18 years of concealments, Western countries are worried that Tehran is using the energy program as a cover for the secret development of nuclear weapons.

The International Atomic Energy Agency's 35-nation board of governors adopted a resolution on Thursday expressing "serious concern" at Tehran's decision to resume uranium conversion activities, and demanding their immediate suspension.

European Union members Britain, France and Germany have taken the lead in the negotiations with Tehran launched after satellite photos revealed the existence of two Iranian nuclear sites in December 2002.