The United States and Iran each said Monday that they control the Strait of Hormuz after a weekend marked by heavy exchanges of fire that spilled across the region and renewed fears that any diplomacy to end the war could collapse.

The latest round was sparked by an Iranian attack on a container ship on Sunday in the strait. Iran says it has managed the waterway—important for international oil and gas shipments—since the US and Israel began the war on Feb. 28. Iran argues it can direct shipping through the strait and potentially charge fees under an interim peace deal reached last month. The US and others dispute Iran’s claim, pointing to principles of freedom of navigation and saying the American military is working to operate an alternative route outside Iranian control.

The dispute grew politically as US President Donald Trump told Fox News that the US was “taking over the Strait,” adding that an 11-hour meeting on Sunday included “everything” being agreed—before Iranian negotiators later called back suggesting changes. Iran also reiterated that it alone must control the waterway.

The fighting raised pressure on mediators trying to revive an interim ceasefire aimed at reopening the strait. Markets reacted as oil prices jumped around 5% at one point before easing later.

At the same time, the US Central Command said its forces struck dozens of targets in Iran, including air defense, radar, missile and drone equipment, and small boats. The EU’s top diplomat, Kaja Kallas, called for the strait to remain open and for freedom of navigation to be respected, while Iran’s Revolutionary Guards rejected the US’s position, calling the strait Iran’s territory.