German Foreign Minister Guido Westerwelle vowed Thursday that the international community will block Iran from obtaining a nuclear weapon, as he underscored Germany's steadfast support for Israel.

"The current Iranian nuclear program represents an enormous danger" not only to Israel but to the region as a whole," Westerwelle told a Jewish advocacy event in Washington.

"We cannot and will not accept an Iranian nuclear weapon... We need substantive and verifiable guarantees that Iran is not pursuing a nuclear weapon."

The West worries Iran is trying to develop an atomic bomb under cover of a civilian energy program, but Tehran insists the program is solely peaceful.

Last month, the so-called P5+1 group -- the five permanent members of the UN Security Council plus Germany -- met in Istanbul with Iranian officials to discuss their concerns, with a further meeting set for May 23 in Baghdad.

Despite Israeli concerns that additional talks would be futile, Westerwelle called for further negotiations with Tehran, stressing that "our unity and our resolve are showing results."

At the same time, he made clear that "our patience is limited. We will not accept playing for time."

Westerwelle expressed concern that "the Iranian regime continues to threaten Israel with annihilation."

"I want you to know that we will continue to stand by Israel's side," he told the audience at the American Jewish Committee's Global Forum.

Israel -- widely considered the Middle East's sole, if undeclared, nuclear power -- has consistently warned that a nuclear-armed Iran would pose an existential threat to the Jewish state, and has refused to rule out a preemptive strike.