US President Donald Trump has demanded Iran surrender as a 60-day agreement aimed at ending the conflict expired without a permanent deal, raising fresh concerns over global oil supplies and the potential impact on fuel-dependent economies such as Tonga.

Trump said Iran should “put up the white flag of surrender” and warned that the United States could take military action against Oman if it obstructed efforts to reopen the Strait of Hormuz.

Oman has been involved in talks with Iran over arrangements for commercial shipping through the strategic waterway.

The 60-day memorandum of understanding between Washington and Tehran expired on Monday without an agreement.

Iran says the United States breached the arrangement and has rejected the significance of the deadline, while Washington has ruled out extending the agreement.

Iranian officials have warned they could adopt a more offensive military posture if diplomacy fails.

The developments matter beyond the Middle East. The Strait of Hormuz is a major route for global oil shipments, and disruption has already pushed crude prices higher. Brent crude rose above US$90 a barrel on Monday as concerns over supply intensified.

For Tonga, renewed pressure on global fuel markets could feed into petrol, diesel, freight and other imported costs.

The National Reserve Bank of Tonga has previously warned that the Middle East conflict could increase fuel, shipping and import costs, putting further pressure on domestic prices.

The immediate question is whether diplomacy can reopen shipping through Hormuz and prevent a wider escalation.

The longer the disruption continues, the greater the risk of another imported fuel and cost-of-living shock is for Tonga.