In recent weeks, Iran has taken aggressive measures to further secure its stockpile of highly enriched uranium, according to five sources familiar with US intelligence.

The sources claim that Iran has destroyed several tunnels and planted explosive mines at entry points to ensure adversaries cannot easily access the uranium, which is enriched to near-weapons-grade capability.

Securing the nearly half-ton of highly enriched uranium from Iran has now become significantly more difficult, hazardous, and time-consuming for any foreign nation than it was just a month ago. At that time, US President Donald Trump had hinted that he might order a military operation inside Iran to seize the material.

According to experts, Iran’s new defensive measures have introduced a major complication into ongoing negotiations with the Trump administration, raising critical questions over who will bear the responsibility and risk of extracting and destroying the material.

CNN reached out to Iran’s diplomatic mission to the United Nations for comment, but did not receive an immediate response. The White House also declined to comment immediately.

President Trump has maintained that taking control of Iran’s highly enriched uranium is currently the top priority for the United States, alongside ongoing negotiations to reopen the Strait of Hormuz.

A US official noted that both nations are moving toward an agreement under which Iran would hand over its uranium to the US, which would then be neutralized and removed from the country.

However, the exact terms of the deal remain murky as statements from both sides conflict. Trump has recently expressed fury over leaks regarding the contents of a draft agreement.

Sources emphasize that extracting the uranium will now be an extraordinarily difficult and dangerous task even for Iran itself, as it would require heavy excavation machinery and risky mine-clearing operations.

Nuclear security expert Scott Roecker warned that if these reports are accurate, recovering the highly enriched uranium will become far more complicated.

"If the negotiations require Iran to consolidate its entire stockpile in one place and hand it over, the onus will primarily fall on them," said Roecker, who served as the director of the Office of Nuclear Material Removal at the US National Nuclear Security Administration (NNSA) from 2017 to 2021.

The primary concern, however, is that Iran might claim a portion of the uranium was destroyed or remains unrecoverable. This would leave the international community unable to verify whether the material could be weaponized in the future.

Experts believe the bulk of this uranium is stored inside collapsed tunnels at Iran’s Isfahan nuclear facility, though the international community suspects some portions are hidden elsewhere.

CNN previously reported that in mid-May, the US had drawn up plans for a ground operation to seize the nuclear materials, but the mission was ultimately aborted due to high risks. Since then, Iran has significantly fortified its highly enriched uranium storage sites.

Trump has previously acknowledged the extreme danger of using military force to recover the uranium. In a May interview with Fox News, he expressed skepticism over whether Iran could ever retrieve the underground material without detection by US intelligence.

"We know exactly what’s going on over there," Trump told Fox News host Sean Hannity. "Nobody has been able to get close to it yet."

However, two sources suggested that Trump’s public signaling of the stockpile as a potential military target likely prompted Iran to aggressively fortify its most valuable nuclear asset.

Even if a deal between the US and Iran is signed swiftly, subsequent detailed negotiations regarding the future of Iran's nuclear program are expected to follow.

To safely remove the uranium from Iran, the US would likely need to deploy a specialized mobile nuclear extraction unit. This unit operates under the NNSA and is based at the Oak Ridge National Laboratory in Tennessee.

Media reports indicate that two top US negotiators, Jared Kushner and Steve Witkoff, recently visited the laboratory.

Nevertheless, experts warn that extracting and transporting the uranium from Iran will be an incredibly intricate and prolonged operation. Even for the most experienced nuclear experts, the process will take considerable time—an assessment shared by Trump himself, who noted that removing the uranium would take at least two weeks.