Washington: Iran has a robust, clandestine nuclear weapons programme that it tried but failed to hide from the world and from its own people, a top White House official has alleged.

White House Press Secretary Sarah Sanders said the recent information released by Israel provided new and compelling details about Iran's efforts to develop missile-deliverable nuclear weapons.

Sanders and US Secretary of State Mike Pompeo issued strong statements yesterday after Israeli Prime Minister Benjamin Netanyahu accused Iran of having secretly pursued a nuclear weapons programme.

Netanyahu said he had conclusive proof that Iran had lied about its nuclear weapons programme.

"These facts are consistent with what the United States has long known: Iran has a robust, clandestine nuclear weapons programme that it has tried and failed to hide from the world and from its own people," Sanders said.

"The Iranian regime has shown it will use destructive weapons against its neighbours and others. Iran must never have nuclear weapons," she said.

Pompeo said the documents obtained by Israel from inside of Iran showed beyond any doubt that the Iranian regime was not telling the truth.

"I have personally reviewed many of the Iranian files. Our nonproliferation and intelligence officials have been analysing tens of thousands of pages and translating them from Farsi. This analytical work will continue for many months. We assess that the documents we have reviewed are authentic," Pompeo said.

The documents show that Iran had a secret nuclear weapons programme for years. It sought to develop nuclear weapons and missile delivery systems and hid a vast atomic archive from the world and from the International Atomic Energy Agency (IAEA), he alleged.

Pompeo said that among the flaws of the Iran nuclear deal was the whitewashing of Tehran's illicit activities related to its military nuclear programme.

Iran had many opportunities over the years to turn over its files to international inspectors from the IAEA and admit its nuclear weapons work. Instead, they lied to the IAEA repeatedly, he alleged.

Pompeo also alleged that Tehran had lied about their nuclear programme to the six nations who negotiated the Iran nuclear deal.

He said what it meant was the deal was not constructed on a foundation of good faith or transparency and was built on Iran's lies.

Iran's nuclear deception is inconsistent with Iran's pledge in the nuclear deal "that under no circumstances will Iran ever seek, develop or acquire any nuclear weapons," he alleged.

"We are therefore assessing what the discovery of Iran's secret nuclear files means for the future of the The Joint Comprehensive Plan of Action (JCPOA).

"Allowing restrictions on Iran's nuclear programme to sunset was a mistake. One has to ask: Why exactly was Iran hiding half a ton of nuclear weaponisation files while implementing the Iran deal?" Pompeo said.

He said that as US President Donald Trump's May 12 deadline to fix the Iran deal was approaching, he will consult with European allies and other nations on the best way forward in light of what they now know about Iran's past pursuit of nuclear weapons and its systematic deception of the world.

Earlier in the day, Trump threatened to end the Iranian deal.

"In seven years that deal will have expired, and Iran is free to go ahead and create nuclear weapons. That's not acceptable. Seven years is tomorrow. That's not acceptable," Trump said, responding to a question during a joint news conference with the visiting Nigerian President Muhammadu Buhari.

"That is just not an acceptable situation. I've been saying that's happening. They're not sitting back idly. They're setting off missiles which they say are for television purposes. I don't think so," he said.

Trump has to make a decision by May 12 on America's continuation in remaining in the deal.

"We'll see what happens. I'm not telling you what I'm doing, but a lot of people think they know. On or before the 12th, we'll make a decision. That doesn't mean we won't negotiate a real agreement. You know, this is an agreement that wasn't approved by too many people. And it's a horrible agreement for the United States," Trump said.