The U.S. and Iran have struggled for weeks to finalize a preliminary agreement to end their war, with Tehran’s demand for early access to tens of billions of dollars in frozen assets emerging as a central obstacle, according to officials and people familiar with the talks.

Talks have been under way for weeks between Tehran and Washington via mediators, with both sides swapping and rejecting the other’s proposals, The Wall Street Journal reported. President Trump continues to threaten to resume the war even as he repeatedly predicts an imminent breakthrough. Sporadic fighting continues.

Iran seeks some $12 billion up front and $24 billion during the 60-day negotiation that would be opened by an initial agreement from its estimated $100 billion in assets frozen by U.S. sanctions, the report said. The assets are mainly revenue from past oil sales and reserves that cannot be transferred to Tehran’s sanctioned banking system without risk of U.S. penalties.

“Twenty four billion dollars is not much for America if he wants to reach an agreement with Iran,” Gen. Mohsen Rezaei, a senior adviser to Iran’s top official, told CNN on Friday. “This is our own, not America’s money.”

Washington says Iran eventually could access some seized assets but the U.S. won’t deliver any money upfront or commit to specific amounts. It is also ruling out broader sanctions relief, such as a waiver that would allow Iran to export oil sanctions-free.

Earlier this week, Secretary of State Marco Rubio said Iran would get no sanctions relief or asset releases until it took clear steps to curtail its nuclear program and hand over its stockpile of enriched uranium after future negotiations. Asked if Iran would get any economic relief just from opening up the Strait of Hormuz to shipping traffic in the first phase of a preliminary deal, Rubio said: “No, that’s not been discussed.”

The fight over assets is haunted by the political fallout of past Iran-U.S. diplomacy and distrust between the sides. The decision by the Obama administration to fly $400 million in Iranian cash to Tehran when the 2015 nuclear deal was implemented, part of a $1.7 billion payment, proved an embarrassing blow to an agreement already under fire. Trump spent years lambasting that deal, saying it provided a legal pathway to an Iranian nuclear weapon, failed to address Iran’s missiles or support for terror, and “enriched the Iranian regime and enabled its malign behavior.”

Now Trump finds himself in a similar position, eager to extract himself from the Iran war, which is deeply unpopular in the U.S., and negotiating with a regime for whom swift access to cash is a priority, the Journal reported.

“In Tehran’s calculus, unfrozen assets are not sweeteners—they are the down payment needed to prove that diplomacy is worth the political risk,” said Ali Vaez, senior adviser at the International Crisis Group, a Brussels-based think tank. “It’s an issue on which Iran is likely to negotiate hardest because it goes to the heart of trust, reciprocity and domestic credibility.”

Iran’s economy remains badly damaged by sanctions. Its exports stay around a third below their 2011 peak, according to World Bank data.

The bulk of the frozen money sits in China from oil revenues. There are also pools of specific, restricted-use assets: $6 billion in Iranian revenues the Biden administration allowed to be transferred to Qatar in 2023 for humanitarian purchases; about $1 billion in Iranian revenues in Oman; and an estimated $15 billion in Iraqi banks from power and natural-gas exports, according to Miad Maleki, a former senior U.S. Treasury sanctions official now at the Foundation for Defense of Democracies.

Late last month, Tehran’s top negotiator, Mohammad-Bagher Ghalibaf, traveled to Qatar, hoping to win assistance from the Gulf emirate to unlock funds, Iranian and Arab officials said. Iranian Foreign Minister Abbas Araghchi said Qatar had recently played a constructive role in financial matters, according to Iranian reports.

One possibility is a credit line from Qatar, collateralized by the Iranian revenue sitting in the country, if permitted by the Trump administration. But U.S. sanctions guidance prohibits any “significant financial service” provided to the Iranian banking system, Maleki noted.

Richard Nephew, a former top State Department sanctions official, said the most straightforward option would be for the Trump administration to allow Iran to start drawing on frozen funds for humanitarian purposes. Another option, he said, would be to provide sanctions waivers for the oil that Iran sells to China, which could free up frozen funds held in China and allow Tehran to legitimately export crude again.

Iranian media have reported that Tehran is pushing for an oil waiver. But it would be a very visible concession by the Trump administration, the Journal reported.

Going deeper: Read MSI’s analysis of asset release dynamics in Iran negotiations →