Dubai. The United States has warned shipping companies they could face sanctions for making payments to Iran in exchange for safe passage through the Strait of Hormuz, escalating pressure in an already volatile standoff between Washington and Tehran.

The alert, issued Friday by the Office of Foreign Assets Control (OFAC), underscores the risks for both US and non-US entities engaging in such transactions, regardless of the payment method.

Roughly one-fifth of global oil and natural gas trade passes through the narrow waterway at the mouth of the Persian Gulf during peacetime, making it one of the world’s most critical energy chokepoints.

Tensions have surged since Iran effectively disrupted normal shipping traffic following the outbreak of conflict with the United States and Israel on Feb. 28. Tehran has since offered some vessels alternative routes closer to its coastline, at times charging fees — a practice now targeted by Washington’s latest warning.

OFAC said the payments could take various forms, including cash, digital assets, informal swaps, offsets, or in-kind contributions such as charitable donations or payments made via Iranian embassies.

“OFAC is issuing this alert to warn US and non-US persons about the sanctions risks of making these payments to, or soliciting guarantees from, the Iranian regime for safe passage,” the agency said. “These risks exist regardless of payment method.”

The US has responded to Iran’s actions by imposing a naval blockade since April 13, preventing Iranian tankers from leaving the region and cutting off a key source of revenue for Tehran’s struggling economy. United States Central Command said 45 commercial vessels have been turned back since the blockade began.

The warning comes as diplomatic efforts to end the conflict remain uncertain. Donald Trump on Friday dismissed Iran’s latest proposal to halt hostilities, signaling continued friction between the two sides.

“They want to make a deal. I’m not satisfied with it, so we’ll see what happens,” Trump told reporters at the White House, without elaborating.

Iran’s state-run IRNA news agency reported that Tehran submitted its proposal to mediators in Pakistan late Thursday. Despite a fragile three-week ceasefire, both sides have accused each other of violations, while the broader standoff continues to rattle global markets, pushing up energy prices and disrupting supply chains.

Negotiations have continued via phone after Trump canceled a planned trip by US envoys to Pakistan. The president has also floated a plan to reopen the strategic waterway, which is vital for Gulf allies exporting oil and gas.

Iranian Foreign Minister Abbas Araghchi has been in contact with regional counterparts and held talks Friday with European Union foreign policy chief Kaja Kallas, as diplomatic channels remain active.

Separately, Iran said Saturday it executed two men convicted of spying for Israel, according to the judiciary-linked outlet Mizanonline. The report identified the men as Yaghoub Karimpour and Nasser Bekrzadeh, saying the country’s Supreme Court upheld their death sentences.

China, meanwhile, called for de-escalation. Fu Cong told reporters that maintaining the ceasefire is the most urgent priority and urged all sides to resume negotiations in good faith to ensure the reopening of the Strait of Hormuz.

Fu added that Chinese Foreign Minister Wang Yi has been in frequent contact with officials from multiple countries, backing mediation efforts led by Pakistan.

He also blamed the conflict on what he described as an “illegitimate war” launched by the United States and Israel, warning of growing economic fallout, particularly for developing nations.