Israel's Mossad spy agency in October 2012 had a less alarmist view of Iran's nuclear program than an assessment delivered by Prime Minister Benjamin Netanyahu at the United Nations just a few weeks earlier, according to a purported secret cable published Monday by two media outlets.

In a landmark speech to the United Nations in September of that year, Netanyahu had brandished a cartoon drawing of a bomb and said Iran was moving ahead with plans that would allow it to potentially build a nuclear bomb within a year or so.

But in the document published Monday by The Guardian and Al-Jazeera, the Mossad is quoted as saying "Iran at this stage is not performing the activity necessary to produce weapons."

The news organizations said the document was an assessment shared with South African intelligence, part of a trove of leaked spy cables sent by several different intelligence agencies, including the CIA and Russian intelligence.

The British newspaper said the documents detail an attempt by the CIA to establish contact with the Islamic militant group Hamas, South Korean intelligence targeting the leader of Greenpeace and South Africa spying on Russia over a joint satellite deal. The paper said it had "independently authenticated" the cache.

An Israeli official said there was "no discrepancy" between Netanyahu's assessment and the unverified leaks. The official spoke on condition of anonymity because he was not authorized to discuss the matter on the record.

The leaks come just days before Netanyahu is scheduled to speak before the U.S. Congress about Iran's nuclear program.

In the 2012 speech, the Israeli leader held a diagram of a cartoon-like bomb showing escalating levels of uranium enrichment. He pulled out a red marker and drew a line across what he said was a threshold which Israel could not tolerate — uranium enrichment to 90 percent, the level needed to make an atomic bomb.

"By next spring, at most by next summer at current enrichment rates, they will have finished the medium enrichment and move on to the final stage. From there, it's only a few months, possibly a few weeks before they get enough enriched uranium for the first bomb," Netanyahu said.

He said his assessment was not based on "military intelligence," but on publicly available U.N. reports.

The purported leaked Mossad cable expresses far less urgency.

"Even though Iran has accumulated enough 5 percent enriched uranium for several bombs, and has enriched some of it to 20 percent, it does not appear to be ready to enrich it to higher levels," the document says.

"Bottom line: though Iran at this stage is not performing the activity necessary to produce weapons, it is working to close gaps in areas that appear legitimate such as enrichment, reactors, which will reduce the time required to produce weapons from the time the instruction is actually given," it said.

Iran reached a landmark interim nuclear deal with world powers in November 2013 under which it converted or diluted its stock of 20 percent enriched uranium. It is negotiating a final deal with the U.S., Britain, France, Russia, China and Germany, with the two sides hoping to agree on a preliminary deal in March and a follow-up pact in June.

Netanyahu has differed with the Mossad in the past, most notably over the effectiveness of a potential military strike on Iran to prevent it from getting atomic weapons.

Israel views a nuclear-armed Iran as a threat to its very existence, citing Tehran's repeated calls for Israel's destruction, its long-range missile program and its support for violent anti-Israel groups like Hezbollah in Lebanon. Iran insists its nuclear program is for purely peaceful purposes like power generation and medical isotopes.

The purported leak comes amid an uproar over Netanyahu's upcoming visit to Washington. He accepted a Republican invitation to address Congress about Iran in early March, but the speech has angered the Obama Administration because it was arranged without consulting the White House, a breach of diplomatic protocol.

The planned speech has drawn fire in Israel as well, coming just two weeks before national elections. Netanyahu has rejected the criticism, saying it is his duty to lobby against the nuclear deal.