IRAN 'CLOSER TO THAT RED LINE'

Netanyahu said Iran had not yet crossed a "red line" he set at the United Nations in September, when he said Tehran should not be allowed to amass enough medium-enriched uranium that, if purified further, would be enough to power a single warhead. He gave a rough deadline at the time of spring or summer 2013.

But he told AIPAC: "Iran is getting closer to that red line and it's putting itself in a position to cross that line very quickly once it decides to do so." However, Netanyahu stopped short of any explicit threat of Israeli military action.

Netanyahu's calculus on Iran is complicated by Israel's unsettled domestic politics. He is still struggling to forge a new coalition government after a surprisingly strong showing by centrist parties in January's elections.

In Kazakhstan, the United States and five other powers offered Iran modest sanctions relief in return for curbing its most sensitive nuclear work. There was no breakthrough but the sides agreed to further talks in early April.

Netanyahu has insisted that Iran, whose leaders have frequently threatened Israel, is using the negotiations to stall for time to develop a nuclear bomb capability. Israel is assumed to be the Middle East's only nuclear-armed power.

"The latest efforts at conciliation and some kind of agreement with the Iranians have failed," Republican US Senator John McCain told the audience earlier. "It's very clear that they are on the path to having a nuclear weapon."

Obama has repeatedly pledged to keep pressure on Iran, but his refusal to take an even stronger stance has contributed to tense dealings with Netanyahu. Even so, the situation has calmed considerably since Obama addressed AIPAC last year and issued a pointed warning against "loose talk" of war with Iran.

A senior Israeli official said that while the Netanyahu government had hoped for a tougher line at the negotiations by the so-called P5+1 - made up of the United States, China, France, Russia, Britain and Germany - it was resigned to awaiting the results of the next round of talks.

Iran may have lessened Israel's immediate sense of urgency by turning some of its 20 percent-pure uranium - which is considered to be only a short technical step away from weapons-grade uranium - into fuel rods for a research reactor.

Netanyahu also made clear Israel's concern about where Syria's stockpile of chemical weapons and other advanced arms might end up in the midst of civil war.

"As the Syrian regime collapses, the danger of these weapons falling into the hands of terrorist groups is very real. Terror groups such as Hezbollah and al Qaeda are trying to seize these weapons as we speak," he said. "We have a common interest in preventing them from obtaining these deadly weapons."