US President Donald Trump’s warning that Washington could destroy Iran’s remaining nuclear facilities within minutes has renewed debate over whether conventional bunker-busting bombs can permanently eliminate Tehran’s underground nuclear infrastructure.
The president said over the weekend that one or two Iranian sites remained potential targets, specifically naming the heavily fortified underground complex known as Pickaxe Mountain.
His comments come as the United States possesses an expanded nuclear arsenal that includes the B61-13, a high-yield gravity bomb that the US Air Force now officially lists as fielded.
Although there is no evidence that Washington intends to use nuclear weapons against Iran, the combination of powerful conventional penetrators and modernised nuclear capabilities raises questions about the military options available to the White House.
The bunker-buster problem
The United States has already demonstrated its ability to attack deeply buried Iranian nuclear facilities.
During Operation Midnight Hammer in June 2025, seven American B-2 stealth bombers deployed 14 GBU-57 Massive Ordnance Penetrator bombs against Iranian nuclear installations.
Each GBU-57 weighs approximately 30,000 pounds and was specifically developed to attack heavily fortified underground structures.
Washington also possesses the 5,000-pound GBU-72 Advanced 5K Penetrator, the older GBU-28 and the 2,000-pound GBU-31 equipped with a BLU-109 penetrating warhead.
However, the destruction of surface infrastructure or underground entrances does not necessarily establish that equipment and nuclear material buried deep inside a mountain have been eliminated.
Iran could potentially restore access, excavate alternative routes or rebuild damaged infrastructure.
This creates a fundamental challenge for Washington: repeated conventional attacks may substantially weaken Iran’s nuclear programme without guaranteeing its permanent destruction.
The B61-13 changes the nuclear equation
The United States has also expanded its nuclear capabilities with the B61-13 gravity bomb.
The National Nuclear Security Administration completed the first B61-13 in May 2025, significantly ahead of its original schedule.
In September 2026, the agency announced that production of critical nuclear components required for the programme had been completed approximately seven months early.
The US Air Force now identifies the B61-13 and B61-12 as fielded variants of its nuclear gravity bomb arsenal.
Unlike the lower-yield B61-12, the B61-13 is designed to provide a higher explosive yield.
The Pentagon has publicly described the B61-13 as providing additional options against certain hardened and large-area military targets.
Its introduction is significant because it expands the range of nuclear capabilities available to the US president.
However, there is no publicly verified indication that the B61-13 has been assigned a role in any operation against Iran.
Washington also possesses the W76-2, a low-yield nuclear warhead carried by submarine-launched ballistic missiles.
Neither the B61-13 nor the W76-2 is publicly documented as a specialized weapon intended to leave underground installations contaminated for decades.
Could radiation make an Iranian facility permanently inaccessible?
One theoretical possibility is that a nuclear attack could cause radioactive contamination severe enough to prevent personnel from safely entering a damaged underground complex for an extended period.
The resulting contamination could complicate repairs, recovery operations and efforts to resume nuclear activity.
But the effects would depend on the circumstances of any detonation, the surrounding environment and the movement of radioactive material.
However, contamination could spread beyond the intended target, potentially affecting civilian populations, agricultural areas and water supplies.
Trump rejects nuclear option as speculation grows
The debate has intensified following claims by US political commentator Tucker Carlson that Washington could be approaching a decision to use a nuclear weapon against Iran.
Carlson suggested that Israeli Prime Minister Benjamin Netanyahu was pressing Trump to launch renewed military action against Pickaxe Mountain.
His claims about a potential nuclear strike have not been independently verified.
Trump, meanwhile, explicitly rejected the use of nuclear weapons against Iran during an October 15 interview with Newsmax.
“I wouldn’t use nuclear. We don’t have to,” the president said.
The White House has not announced any change to that position.
Recent reporting has focused primarily on conventional military operations, while Trump has indicated that negotiations with Tehran remain possible.
Secretary of State Marco Rubio has also said that no final decision has been made on renewed strikes.
A dangerous escalation
The use of even a relatively low-yield nuclear weapon would represent an extraordinary escalation.
It would break the precedent against nuclear weapons use in warfare that has stood since the United States bombed Hiroshima and Nagasaki in 1945.
Such an attack could also provoke Iranian retaliation, destabilise the wider Middle East and raise serious concerns about the future of nuclear deterrence.
Even without nuclear escalation, a renewed bombing campaign could trigger further attacks against American military installations and regional energy infrastructure.
For Washington, the central strategic challenge remains unchanged.
The United States has demonstrated that it can severely damage Iranian nuclear installations using conventional weapons, but proving that the country’s nuclear capabilities have been permanently eliminated is considerably more difficult.
The arrival of the B61-13 adds another capability to America’s nuclear arsenal, but its existence does not establish that Washington intends to use it in the current confrontation.
The question is no longer simply whether the United States can strike Iran’s remaining underground nuclear sites. It is whether any military attack can guarantee that those facilities — or the expertise behind them — will never be used again.
