This time, Israel's fears over Iran's intention to build a nuclear bomb really may be valid. Or not. And for better or worse, it will be U.S. President Donald Trump making the decision about what facts to accept or to reject.

For most of his nearly 20 years leading Israel, Israeli Prime Minister Benjamin Netanyahu has been stoking international concerns that his country faces the threat of "nuclear annihilation" if Iran is able to build an atomic weapon.

As early as 1996, he proclaimed: "Time is running out." Sixteen years later, in 2012, Netanyahu stood before the UN with an almost cartoon-like drawing of a round bomb with a lit fuse, urging the international community to stop Iran's ayatollahs before it was too late.

Finally, seven nights ago, Netanyahu gave the order to attack Iran directly, stating that the mission is to take out Iran's institutions, facilities and scientists related to its nuclear program.

"If not stopped, Iran could take steps to produce a weapon in a very short time," Netanyahu said in a video statement justifying his decision.

Israel's sweeping campaign of airstrikes in and around Tehran has wiped out the top tier of Iran's military command, damaged its nuclear capabilities and killed hundreds. Iranian retaliatory strikes, meanwhile, have killed at least two dozen civilians in Israel.

But finishing the job of destroying Iran's nuclear program may be beyond Israel's capabilities. With some key components and facilities fortified up to 80 metres underground, it may require weaponry and heavy bombs possessed only by the U.S. 

Trump — under intense pressure domestically from many Republicans who want him to intervene, and perhaps an equal number who want him to stay out of the fight — said Thursday he'll make a decision within the next two weeks on what course to take, to give diplomacy with Iran more time.

At least one former top Israeli intelligence official believes the evidence of both Iran's capability and intent to produce such a weapon of mass destruction is incontrovertible.

"I think the last report of the IAEA (International Atomic Energy Agency) says that Iran has more than 400 kilograms of 60 per cent enriched uranium, which, if you enrich it to 90+, is enough for 10 nuclear devices," said Sima Shine, a former officer at Israel's spy agency Mossad who is now with the Institute for National Security Studies in Tel Aviv.

The only outstanding issue was Iran's willingness to build a bomb, she said, given that such a move would surely invite a devastating Israeli response.

"Our impression was that in the last year, the interest of Iran to go the extra mile and actually reach a nuclear, military nuclear capability has changed, if we compare to its previous use," Shine told CBC News.

She said since the Oct. 7, 2023 assault on Israel, Israeli attacks have critically weakened Iran's key proxy militias in Gaza and Lebanon — Hamas and Hezbollah. That's left Iran deeply weakened, she said, forcing the ayatollahs to change Iran's calculations about the necessity of building a nuclear weapon to project-strength.

Military enrichment?

Other Iran watchers in the West share Shine's assessment.

"There is no purpose at all for having that level of nuclear enrichment and that stock of enriched uranium other than military," said John Sawers, former chief of Britain's Secret Intelligence Service MI6, speaking to the BBC.

Israeli authorities have suggested their own intelligence efforts have also turned up proof of Iran's intentions, beyond what the IAEA has reported.

Quoting unnamed sources, the Wall Street Journal said Israeli agents learned of Iran's interest in developing and perfecting chain-reaction explosions, which are required for nuclear weapons.

Megan Sutcliffe, an analyst with the private intelligence firm Sibylline, said that beyond the actual manufacture of a nuclear device, it's also possible the Iranians were working on improving missiles and rockets that could carry a bomb.

"The IAEA does not monitor this," she said. "And so the intelligence that Israel is likely referring to is something to do with Iran possibly making strides toward testing the viability of some form of delivery system."

Doubts persist

Still, in the absence of that information being shared publicly, doubts persist about both Iran's intentions and its capabilities.

Tulsi Gabbard, Trump's director of national intelligence, told Congress earlier this year that U.S. intelligence agencies did not believe Iran had made a decision to weaponize its nuclear program.

The Washington-based Arms Control Association, a think-tank that promotes arms control and diplomacy, issued a statement earlier this week, denouncing any U.S. involvement in Israel's war against Iran.

"There was no imminent threat that Iran was weaponizing its nuclear program before Israel's attack began," it wrote.

The group argued U.S. intervention could have the opposite effect — strengthening Tehran's resolve and leading it to weaponize its nuclear program, if it is not completely destroyed or is eventually rebuilt.

And while the chief of the IAEA ruled last week that Iran was in breach of its non-proliferation obligations for a lack of disclosure, Raphael Grossi also said the global nuclear watchdog had seen no evidence that Iran's enriched uranium was being steered toward military or non-civilian purposes.

"We cannot say that we at the IAEA have enough credible elements which would be pointing directly at this," he said.

In an interview with CBC News, Iran's ambassador in Geneva reiterated his country's right to have a nuclear program and to develop enriched uranium from it.

"There is no evidence of Iran moving toward military nuclear activities," said Ali Bahreini. "Our nuclear activities are peaceful."

Enriched uranium can also be used to produce medical isotopes or as fuel for nuclear power plants.

WATCH | About That on how the U.S. might be pulled into the Israel-Iran war: 

How deep will the U.S. be pulled into the Israel-Iran war? | About That

U.S. President Donald Trump has consistently denied his country's involvement in the intensifying conflict between Israel and Iran. But Andrew Chang explains the role the U.S. has already played. Then, Will South Korea’s new leader save the country?

Israel's nuclear program 

Israel is widely believed to have had its own nuclear weapon capabilities for several decades, although the country's official policy is deliberate ambiguity with regards to the existence of such a program.

"Essentially, it is widely acknowledged that Israel does have a nuclear arsenal and that they also have … a nuclear submarine, which gives them a second-strike capability; the ability to respond to a nuclear weapon being fired toward them," said Sutcliffe.

Israel has not signed the Nuclear Non-Proliferation Treaty (NPT) and has not accepted IAEA safeguards on some of its principal nuclear activities, the Center for Arms Control and Non-Proliferation notes.

The Washington-based group also notes that "the lack of clarity surrounding an Israeli nuclear weapons program is a key obstacle to establishing a weapons of mass destruction free zone in the Middle East."

Nonetheless, most countries — including Israel's current and historic adversaries — have generally accepted the country's nuclear policies.

Sutcliffe said she believes the different treatment between Iran and Israel on their nuclear programs stems from long-standing, repeated statements from Iran's leaders about their intent to destroy Israel, if given the opportunity.

"Iran has characterized itself as being a threat to Israel — both through its direct actions, but also through its support of proxies to threaten Israel," she said.

Iran's leadership has expressed strong support for Palestinians being free of Israeli occupation, and it was a strong financial and military supporter of Hamas in Gaza.

The Palestinian Authority in the West Bank, however, has repeatedly said Iran's support of Hamas has not helped the Palestinian cause, nor been beneficial to the establishment of a Palestinian state alongside Israel.

For both Trump and Netanyahu, the decision over which intelligence and analysis to go with will have immense consequences — for Israel and far beyond.

Gershon Baskin, a longtime advocate for peaceful coexistence between Arabs and Israelis and fierce Netanyahu opponent, said he believes that most Israelis hope Trump jumps into the war on their side.

"They're living this kind of hubris that Israel can do whatever it wants, wherever it wants, at any time," said Baskin referring to public sentiment over the damage Israel's military has inflicted on Iran's nuclear facilities and the assassinations of its nuclear scientists.

But he cautioned domestic politics could shift quickly against Netayahu and his efforts to reign in his Iranian enemies, should his calculations over damaging Iran's nuclear program backfire.

"When we see more damage and more casualties, there'll be a shift of mood in Israel about the justification for the war, and the need to carry on this war. It's inevitable."