Israeli Prime Minister Binyamin Netanyahu has said that diplomacy has so far failed to deter Iran from pursuing its nuclear programme, warning it was getting closer to crossing a crucial "red line."

 "Iran enriches more and more uranium, it installs faster and faster centrifuges," and it is "running out the clock" on diplomatic efforts to prevent the Islamic republic from obtaining nuclear capability, Netanyahu said on Monday.

 "We have to stop its nuclear enrichment programme before it's too late," he warned in a speech via satellite from his office in Israel to the American Israel Public Affairs Committee, the largest pro-Israel lobby in the US.

 The Israeli prime minister warned that leaders in Tehran had opted to "just grit their teeth" through punishing international sanctions and pursue their nuclear plan, come what may.

 "It's still not crossed the red line I drew with the United Nations last September," Netanyahu said, referring to the point at which Israel believes Iran would be able to build a nuclear weapon.

 "But Iran is getting closer to that red line, and it is putting itself in a position to cross that line very quickly once it decides to do so."

 "And I have to tell you," Netanyahu added, "from the bottom of my heart, and the clarity of my brain, words alone will not stop Iran."

 "Diplomacy has not worked," he said, stressing that Iran's leaders have "used negotiations, including the most recent ones, to buy time to press ahead with its nuclear programme."

 Sanctions alone will not stop Iran, Netanyahu said. They must be "coupled with a clear and credible military threat if diplomacy and sanctions fail."

 'Not bluffing'

 Meanwhile, at the same conference, US Vice President Joe Biden said that President Barack Obama is 'not bluffing' about America's determination to stop Iran from getting a nuclear weapon.

 "The president of the United States cannot and does not bluff. President Barack Obama is not bluffing," he told AIPAC in a speech.

"We're not looking for war. We're ready to negotiate peacefully. But all options including military force are on the table," said Biden.

"While that window is closing, we believe there is still time and space (for diplomacy)," he added.

Biden said that a nuclear bomb in Iranian hands would be an "existential threat" to Israel, poses danger to other US allies in the Middle East and would destabilize the world.

"We have a shared strategic commitment. Let me make clear what that commitment is: It is to prevent Iran from acquiring a nuclear weapon, period," he said to loud applause from AIPAC, which has gathered some 13,000 activists in Washington this week.

Western officials said Iran had yet to do anything concrete to allay their concerns about its nuclear aspirations.

The United States, China, France, Russia, Britain and Germany offered modest relief from economic sanctions in return for Iran reining in its most sensitive nuclear activity but made clear that no breakthrough was in the offing quickly.

PHOTO CAPTION

Israeli Prime Minister Benjamin Netanyahu chairs the weekly cabinet meeting at his Jerusalem office on March 3, 2013.

Aljazeera