Secretary of State Marco Rubio said Friday that back-channel negotiations with Iran show “a little bit of movement,” but cautioned against optimism as a critical dispute over the Strait of Hormuz threatens diplomatic progress.

Rubio’s measured assessment came as Pakistan’s Army Chief Field Marshal Syed Asim Munir prepared to travel to Tehran for consultations, continuing Islamabad’s role as intermediary between Washington and Iranian officials. The comments reflect cautious engagement despite significant obstacles in ongoing discussions.

The Strait of Hormuz Stalemate

Iran’s proposal to establish what it calls a “tolling system” for commercial vessels transiting the Strait of Hormuz has emerged as a major barrier to negotiations. Rubio called the proposal unacceptable, stating “it would make a diplomatic deal unfeasible if they were to continue to pursue that.”

The strategic waterway handles nearly one-fifth of global oil exports, and any disruption affects markets worldwide. Iran maintains it will only fully reopen the passage if allowed to charge transit fees, a demand the State Department has flatly rejected.

Preparing for Diplomatic Failure

Rubio warned that if Tehran refuses to compromise on the strait, the United States must have contingency plans ready. “If Iran keeps digging in, Washington has to have a Plan B,” he said.

The warning underscores U.S. concerns that diplomacy could collapse, leaving unresolved tensions across the Middle East. The Trump administration has signaled cautious optimism about reaching a deal within weeks, according to statements from officials.

Regional Escalations Continue

Israeli airstrikes in Lebanon have killed more than 3,100 people since March 2, according to Lebanon’s health ministry, as conflict with Iran-backed Hezbollah persists. A U.S.-brokered ceasefire imposed in mid-April has failed to halt hostilities.

The European Union moved Friday to expand sanctions targeting those responsible for the Strait blockade, implementing travel bans and asset freezes. EU officials declared the closure “contrary to international law.”

Iran’s Counter-Proposal

Iran introduced a new mechanism called the Persian Gulf Strait Authority to regulate maritime transit, according to Iranian state media. The system requires vessels to request authorization and comply with transit rules before crossing the waterway.

U.S. officials have indicated the proposal is unlikely to gain acceptance from international shipping partners or Western governments, further complicating negotiations.