Ceasefire under strain after U.S. seizes Iranian cargo ship

Concerns are mounting over the durability of the ceasefire between the United States and Iran after Washington said it had seized an Iranian cargo vessel accused of breaching its maritime blockade, prompting a warning of retaliation from Tehran.

According to the U.S. military, forces opened fire on an Iranian-flagged ship following a prolonged standoff in waters near the Strait of Hormuz, disabling its engines before troops boarded the vessel. U.S. Central Command said marines descended from helicopters and took control of the ship.

U.S. President Donald Trump confirmed the operation in a social media post, saying American forces had “full custody” of the vessel and were inspecting its cargo.

Iranian authorities condemned the seizure, describing it as “armed piracy.” A military spokesperson, quoted by state media, warned that Iran’s armed forces would respond. Officials said the ship had been en route from China to the Iranian port of Bandar Abbas.

Ceasefire and talks in doubt

The incident has cast doubt on efforts to sustain a fragile ceasefire set to expire on Tuesday. Hopes for a broader agreement also appeared uncertain after Iranian state media reported that Tehran would not take part in a planned second round of negotiations.

Iranian officials cited ongoing U.S. blockade measures, escalating rhetoric, and what they described as shifting demands from Washington. First Vice President Mohammadreza Aref said Iran would not accept restrictions on its oil exports while others benefited from open energy markets.

“If Iran’s oil is restricted, others should not expect full security,” he said in remarks carried by state media.

Preparations for uncertain negotiations

Despite the tensions, diplomatic activity is continuing. U.S. envoys are expected to travel to Islamabad, which has been acting as a key mediator. However, uncertainty remains over the composition of the U.S. delegation and whether talks will proceed as planned.

Security measures in Islamabad have been stepped up ahead of the anticipated visit, with restrictions imposed on transport and heightened protection around key venues.

Iran’s parliament speaker Mohammad Baqer Qalibaf had earlier indicated that while some progress had been made in initial discussions, significant gaps remain, particularly over nuclear issues and maritime security.

Global market impact

The developments have unsettled global markets. Oil prices rose sharply amid fears that the ceasefire could collapse, further disrupting flows through the Strait of Hormuz — a critical route for roughly one-fifth of the world’s oil supply.

The conflict, now in its eighth week, has already caused major disruptions to regional energy production. Countries including Saudi Arabia, Iraq, Kuwait and the United Arab Emirates have seen significant declines in output.

Escalating rhetoric

Tensions have been further heightened by increasingly sharp rhetoric. President Trump has warned that the United States could target key Iranian infrastructure if negotiations fail, while Iranian officials have threatened retaliatory strikes against regional energy and utility facilities if attacked.

The war, which began in late February, has triggered one of the most severe shocks to global energy markets in recent history and raised fears of broader regional escalation.