Interim Prime Minister Ehud Olmert on Sunday urged the international community to work against the Iranian nuclear program, saying Tehran's ambitions threaten not only Israel but all of Western civilization.

Israel has long identified Iran as its biggest threat, and these concerns have grown amid repeated calls by Iran's hard-line president, Mahmoud Ahmadinejad, for Israel's destruction.

"From the point of view of seriousness this tops the state of Israel's list, it is potentially an existential threat," a government statement quoted Olmert telling the weekly Cabinet meeting.

"The Iranian nuclear program should concern many countries, especially those with global responsibility," Olmert said, adding that the international front against Iran should include the United States, Europe and other Western countries.

Iran this month announced it enriched uranium for the first time, a process that can be used to build atomic weapons as well as for electricity generation.

Iran on Sunday said its nuclear program is irreversible, rejecting a U.N. Security Council deadline to end the enrichment.

The U.S., Israel and some Western allies charge Iran is using the program as a cover for weapons production. Iran says it is designed only for power generation.

Israel also accuses Iran of supporting Palestinian militant groups.