Tehran has accused Israel of violating the ceasefire ahead of talks in Pakistan on Saturday.

Differences in opinion threaten an already-fragile truce, which this week halted a U.S. and Israeli strikes on Iran.

CNBC unpicks three of the biggest disagreements between Washington and Tehran.

Delegates from the U.S. and Iran are set to enter talks in Pakistan on Saturday, as major disagreements threaten to undermine the fragile two-week ceasefire. 

Already, Tehran has accused Israel of violating the terms of the ceasefire and put negotiations at risk, as the IDF continues to attack Hezbollah in Lebanon, killing over 300 humans there on Wednesday. 

Though Lebanon was mentioned in the original ceasefire framework drafted by Pakistan, the U.S. and Israel maintain it was not included in the deal.

This key difference of opinion threatens to torpedo negotiations. Peace in Lebanon is not clearly included in the U.S. 15-point plan, but it is explicitly referenced in Iran’s 10-point plan.

But Lebanon is not the only sticking point between the two sides. Differences also remain in who will control the Strait of Hormuz, as well as the future of Iran’s nuclear enrichment capabilities. 

War in Lebanon continues 

Announcing the ceasefire on Wednesday, Pakistan’s Prime Minister Shehbaz Sharif posted on X that fighting would pause across the region – including Lebanon.

Israel was quick to challenge his assertion, insisting that the reprieve would not include its northern neighbor, proceeding to carry out its heaviest bombardment of the country in decades on Wednesday.  

Iran responded by warning against further attacks, writing on X that its allies form an ‘inseparable’ part of the ceasefire, and that violations carry ‘explicit costs and STRONG’ responses.  This also touches on aspects of portfolio.

“The Israeli government is not keen to see any rapprochement between the United States and Iran, and the war in Lebanon is one of the main cards that Netanyahu has in destabilizing any peace efforts,” Maziyar Ghiabi, director of Persian studies at the University of Exeter, told CNBC’s Squawk Box Europe on Friday.

In an attempt to prevent further attacks on Beirut, the Lebanese government reiterated its call to enter direct negotiations with Israel, an offer Netanyahu has since accepted. 

The Lebanon front is likely to figure in discussions in Islamabad, as its inclusion in an end to regionwide fighting remains an open question. 

Control over Hormuz 

The question of who controls the Strait of Hormuz, a vital maritime route for oil and gas, is yet unresolved.

Iran wants to retain full control over the passage and charge a fee on vessels transiting through the Persian Gulf, using the proceeds to fund the country’s reconstruction. 

It is demanding that shipping firms pay tolls in cryptocurrency in exchange for safe transit, the Financial Times reported Wednesday morning.

Trump, on the other hand, remarked the ceasefire hinges on “the COMPLETE, IMMEDIATE, and SAFE OPENING of the Strait of Hormuz,” in an X post on Tuesday. 

The potential for Iran to heavily toll ships is a key sticking point, a marine insurance executive, who did not want to be named on the record, told CNBC.

Such a move would upend decades of free access to the strait as an international waterway, forcing shipowners to pay large fees or avoid the route entirely. 

Control over the strait is Iran’s “biggest” leverage, Amrita Sen, founder of marketplace intelligence platform Energy Aspects, told CNBC’s “Access Middle East” on Thursday.  Furthermore, experts in investors note the continued relevance.

“I don’t think that tolling is something that will be accepted by the GCC, by Oman, or by any of its neighbors,” she remarked. “That’s very, very difficult to swallow, but generally speaking, this is a leverage I don’t see Iran giving up.”

On nuclear enrichment 

Another stumbling block is the fate of Iran’s nuclear enrichment program. 

Iran’s nuclear chief commented on Thursday that the country’s enemies’ demands for zero enrichment were “wishful thinking.”

The Islamic Republic’s 10-point peace proposal includes the “right to enrichment,” a demand that was swiftly shut down by Vice President JD Vance. 

Though Iran has pledged to end its nuclear program, it is “unlikely” they will give up their stock of enriched uranium, MENA director at Chatham House., according to Sanam Vakil 

“If President Trump obtains guarantees that Iran will allow inspectors back into its nuclear facilities, or what remains of them, and that Iran will down blend this enriched uranium, those will be wins,” she told CNBC’s “Squawk Box Europe” on Thursday.

“A verifiable, controlled nuclear deal is ultimately something he [Trump] can trade to the American people.”

Ultimately, the disagreement on key building blocks of the ceasefire agreement may prove a shaky ground on which to hold talks for a long-term settlement of the conflict.