Iranian Supreme Leader Ayatollah Mojtaba Khamenei has issued a directive that the country’s almost weapons-grade uranium should not be shipped abroad, Reuters reported, citing two senior Iranian sources.

The report came as U.S. President Donald Trump reiterated his stance that the U.S. will seize Iran’s uranium holdings. Trump has set stopping Iran’s nuclear activities as the main objective of his war against the country, insisting that Tehran cannot be allowed to acquire a nuclear weapon.

Iran, on the other hand, has repeatedly claimed that its uranium will only be used for peaceful purposes. Disagreements over the uranium remained a key sticking point in peace negotiations between Washington and Tehran. 

While a fragile ceasefire between the two sides remained in place, efforts aimed at resolving the impasse so far proved to be unsuccessful.

Trump said the U.S. was in the “final stages” of a potential draft peace agreement, although he raised the specter of a re-escalation in hostilities, warning that “we’re going to do some things that are a little bit nasty” should a deal not be reached.

Iran, for its part, has said that it is reviewing Washington’s most recent position on concluding the conflict, but is ready to respond to more strikes with its own crushing barrage.  

Earlier this week, Trump said he had postponed a proposed military operation against Iran, and that negotiations with the country were going well.

Trump also signaled that he was willing to wait a “few days” for a deal, but warned of more military action against Iran if a peace deal was not achieved. The U.S. president said the Iran war was in its “final stages.” 

Iran’s nuclear activities remained a major point of contention, with Trump reiterating that the country could not be allowed to acquire a nuclear weapon. 

Crucially, shipping traffic in the Strait of Hormuz — a major focus point in the war — remained at a fraction of pre-war levels, amid little progress towards a resolution. Iran was reportedly preparing to charge tolls for passage through the channel, and has included the idea in its peace proposals.