Israeli Prime Minister Benjamin Netanyahu says a "clear and credible" military threat is needed to stop Iran from building a nuclear weapon.
Speaking from Jerusalem by satellite to a pro-Israeli lobbying group in Washington, Mr. Netanyahu said words and sanctions alone will not stop Iran.
He said despite diplomacy and sanctions, Iran is getting closer to what he calls the "red line" -- the point where it may be ready to build its first nuclear weapon.
Mr. Netanyahu reiterated that Iran is using negotiations, including recent talks in Kazakhstan, as a tactic to buy time .
U.S. Vice President Joe Biden also spoke to the American Israel Public Affairs Committee Monday. He said all options remain on the table concerning Iran. But Mr. Biden said while time is running out for diplomacy, a negotiated solution is still possible.
Iran denies it wants to build nuclear weapons and says its nuclear program is for peaceful purposes only.
The chief of the International Atomic Energy Agency, Yukiya Amano, said Monday said that without more cooperation from Iran, his inspectors cannot conclude that all nuclear material is for peaceful activities. Amano said further negotiations with Iran must "proceed with a sense of urgency."