Iran Rejects U.S. Red Line on Enrichment, Raising Stakes for Trump

Having Vowed to End Tehran’s Path to Nuclear Weapons, Trump Faces a Difficult Choice of Compromise or Confrontation

Winfield Myers

Iran’s Supreme Leader Ali Khamenei.

With Iran’s ruler Ali Khamenei forcefully rejecting the United States’ demand to halt uranium enrichment, the path for negotiations has become more fraught. What comes next for the Trump administration, which entered this process two months ago with impatience and a demand for swift results?

In a May 20, 2025, speech, Khamenei issued his strongest public defiance yet: “It’s outrageous arrogance to say Iran cannot enrich uranium.” However, the Persian phrase he used—“ghalate ziadi”—was far more scornful, carrying a deliberately disrespectful tone aimed at the United States.

Nearly two months have passed since negotiations were announced, yet no tangible outcome has emerged.

From the outset, the Trump team signaled it would not tolerate prolonged negotiations like those under Presidents Barack Obama or Joe Biden. During his Middle East tour on May 16, President Donald Trump revealed that Washington had sent a new proposal to Tehran. He also issued a warning: “They have a proposal. More importantly, they know they have to move quickly or something bad—something bad’s going to happen.”

Nearly two months have passed since negotiations were announced, yet no tangible outcome has emerged. Uranium enrichment has become the central and most contentious issue. In recent days, the United States has drawn a firmer red line: Iran cannot maintain any enrichment capability.

With that backdrop, Khamenei’s stance raises the question: Why would he risk collapsing the talks under threat of possible military action?

Two possible explanations emerge. First, the withdrawal of U.S. air and naval reinforcements from the region—originally seen as a direct warning to Iran and its Houthi allies—now may be interpreted in Tehran as a signal that Washington is unwilling to strike Iran’s nuclear sites if talks fail. Khamenei may see this as a sign of weakness.

Second, Tehran may sense indecision in Washington. Despite strong public messaging, Politico reported on May 16 that unnamed European diplomats and a former Trump official believe the administration may be privately considering a concession—allowing Iran to retain limited low-level enrichment.

Khamenei, under pressure from serious regional setbacks and Trump’s return to power, may be trying to hold his ground while probing for any sign of U.S. flexibility to avoid a total rollback of Iran’s nuclear program.

For Trump, already unable to bring a ceasefire to Ukraine, failure with Iran would be politically damaging. Having promised that Tehran will not be allowed any path to nuclear weapons, he now faces a difficult choice: either allow a face-saving compromise or escalate the confrontation.

Short of military action, the most potent remaining lever is economic pressure.

Short of military action, the most potent remaining lever is economic pressure. The U.S. Navy could begin seizing Iranian tankers smuggling oil to China. But such a move risks Iranian retaliation against shipping in the Red Sea or the Persian Gulf—potentially triggering a military confrontation.

One way or another, the Trump administration is approaching a moment of decision. Arab states in the region, which hold considerable influence over Trump, appear reluctant to see a military conflict—unless they can be sure to avoid the fallout. On the other hand, nearly all Republican senators recently signed a letter urging the president to prevent any deal that allows Iran to retain enrichment capability.

Any new agreement that permits even limited enrichment would resemble the 2015 Joint Comprehensive Plan of Action—the very arrangement Trump once ridiculed and rejected.

Mardo Soghom was a journalist and editorial manager at Radio Free Europe/Radio Liberty for three decades, overseeing the Iran and Afghanistan services until 2020, and was chief editor of the Iran International English website.
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