The U.S. and Iran are negotiating over a three-page plan to end the war, with one element under discussion being that the U.S. would release $20 billion in frozen Iranian funds in return for Iran giving up its stockpile of enriched uranium, according to two U.S. officials and two additional sources briefed on the talks, Axios reported.

There has been steady progress in the talks this week, though significant gaps remain. A deal on these terms would bring the war to a close, while potentially generating backlash from Iran hawks.

US President Trump said Thursday that U.S. and Iranian negotiators would likely meet this weekend for a second round of talks to try to seal the deal.

The talks are expected to take place in Islamabad, likely on Sunday, according to a source familiar with the mediation efforts.

Pakistan is mediating the negotiations, with behind-the-scenes support from Egypt and Turkey.

According to two sources, the U.S was ready in an earlier stage of the negotiations to release $6 billion for Iran to purchase food, medicine and other humanitarian supplies. The Iranians demanded $27 billion.

The latest number discussed by the U.S. and Iran is $20 billion, the sources said. One U.S. official said that was a U.S. proposal. The other U.S. official described the cash-for-uranium concept as "one of many discussions."

Meanwhile, the U.S. asked Iran to agree to ship all its nuclear material to the U.S., while the Iranians only agreed to "down-blend" it inside Iran.

Under a compromise proposal now under discussion, some of the highly enriched uranium would be shipped to a third country, not necessarily the U.S., and some of it would be down-blended in Iran under international monitoring.