Lieberman said President Obama has retained the military option to end the nuclear program -- though the president has said diplomacy must be tried first.
Speaking to the American Israel Public Affairs Committee, the pro-Israeli U.S. senator said the Iranian "regime must hear a message from us and we must state it loud and clear: Either you peacefully negotiate an end to your illicit nuclear activities, or they will be ended for you by military attack."
"It's time for us to make an iron-clad pledge, which will be heard both by our friends and enemies in the Middle East and throughout the world, the United States will prevent Iran from acquiring a nuclear weapons capability by peaceful means if we can, but with military force if we absolutely must," Lieberman said to applause.
Lieberman said he and two other senators have "introduced a non-partisan resolution that says, when it comes to Iran, all options must be on the table, except one option. And that is, containment. It won't work.
"That's precisely what President Obama has said. Now it's time for the other end of Pennsylvania Avenue to say the same thing."
He said: "The Iranian nuclear program is a threat to the entire world, but especially to the United States, Israel and the Arab nations of the Middle East. If Iran is allowed to acquire a nuclear weapons capability, it will set off a cascade of nuclear proliferation as other countries in the region seek atomic arsenals of their own. If Iran is allowed to acquire a nuclear weapons capability, it will make its terrorist proxies, groups that already have the blood of thousands and thousands of Americans, Israelis and Arabs on their hands, infinitely more dangerous."
Lieberman said a nuclear-armed Iran "will be able to bring the global economy to its knees. Whenever it wants. If you think gas prices are high now in our country, imagine what will happen if Iran could back up its threat to close the Strait of Hormuz with a nuclear weapon. This is a future we cannot afford. It is a future we can and must prevent."