Israel's Prime Minister has unveiled what he says is a "half ton" of Iranian nuclear documents collected by Israeli intelligence, claiming the trove of information proves that Iranian leaders covered up a nuclear weapons program before signing a deal with the international community in 2015.

Key points: Benjamin Netanyahu says he has 100,000 secret files to prove Iran lied

Benjamin Netanyahu says he has 100,000 secret files to prove Iran lied Donald Trump says Iran is "not sitting back idly"

Donald Trump says Iran is "not sitting back idly" Iran's semi-official news agency dismisses "propaganda show"

In a speech delivered in English and relying on his trademark use of visual aids, Benjamin Netanyahu claimed that the material showed that Iran could not be trusted, and encouraged US President Donald Trump to withdraw from the deal next month.

"Iran lied big time," Mr Netanyahu declared.

The Israeli leader showed pictures and videos purporting to be of historic secret Iranian nuclear facilities, as well as Iranian documents and plans to develop atomic weapons.

"First, Iran lied about never having a nuclear weapons program. One-hundred-thousand secret files prove it did," Mr Netanyahu said.

"Second, even after the deal, Iran continued to preserve and expand its nuclear weapons knowledge for future use.

"Third, Iran lied again in 2015 when it didn't come clean to the IAEA [International Atomic Energy Agency] as required by the nuclear deal."

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Mr Netanyahu said he would share the newly uncovered information with Western allies and the international nuclear agency.

"After signing the nuclear deal in 2015, Iran intensified its efforts to hide its secret files," he said.

"In 2017 Iran moved its nuclear weapons files to a highly secret location in Tehran."

Mr Netanyahu referred to a secret Iranian nuclear project, codenamed "Amad", which he said had been shelved in 2003, but he said work in the field had continued.

He said Israel had obtained some 55,000 pages of documents and 183 CDs of secret information about "Amad".

Mr Netanyahu said the material was gathered from a vaulted Iranian facility a few weeks ago "in a great intelligence achievement".

US Secretary of State Mike Pompeo later said the US had been aware of the documents "for a while" and that he and Mr Netanyahu discussed them during their meeting in Tel Aviv on Sunday.

Speaking with reporters while flying back to the US, Mr Pompeo said although the existence of Iran's nuclear arms program had been public knowledge for years, the documents gave new detail about its scope and scale and prove Iran was lying when it claimed never to have been pursuing nuclear weapons.

"This will belie any notion that there wasn't a program," Mr Pompeo said.

He issued a statement later saying Iran also lied to the six nations with which it negotiated the nuclear agreement.

"What this means is the deal was not constructed on a foundation of good faith or transparency," the statement said.

"It was built on Iran's lies."

Benjamin Netanyahu says the documents show Iran cannot be trusted. ( AP: Sebastian Scheiner )

Ahead of the announcement, Iran's foreign minister, Mohammad Javad Zarif, belittled Mr Netanyahu in a tweet, saying: "The boy who can't stop crying wolf is at it again".

Iran's deputy foreign minister and senior nuclear negotiator, Abbas Araghchi, called Mr Netanyahu's presentation "childish and ridiculous" and said the purported evidence was "fake and fabricated".

Iran has denied ever seeking nuclear weapons.

Iran's semi-official Fars news agency, believed to be close to the hard-line Revolutionary Guard, dismissed Mr Netanyahu's speech as a "propaganda show".

'They're setting off missiles': Trump

Israeli Prime Minister Benjamin Netanyahu has a welcome partner in US President Donald Trump. ( Reuters: Ronen Zvulun )

The Israeli Prime Minister's presentation, delivered on live TV from Israeli military headquarters in Tel Aviv, was his latest attempt to sway international opinion on the nuclear deal.

The agreement offered Iran relief from crippling sanctions in exchange for curbs on its nuclear program.

Mr Netanyahu has found a welcome partner in Mr Trump, who has called the agreement "the worst deal ever".

Mr Trump has signalled he will pull out of the agreement unless it is revised, but he faces intense pressure from European allies not to do so.

On Monday, the US President declined to say whether the US would withdraw from the accord before a May 12 deadline for a decision, saying: "We'll see what happens."

But he expressed his dissatisfaction with the pact.

"That is just not an acceptable situation," Mr Trump said.

"They're not sitting back idly. They're setting off missiles, which they say are for television purposes. I don't think so.

"That doesn't mean we won't negotiate a real agreement."

AP/Reuters