The United States military launched a naval blockade of all Iranian Gulf ports and coastal areas on Monday after weekend negotiations in Pakistan ended without a deal, dramatically escalating the ongoing US-Israel war on Iran. US Central Command announced the blockade would take effect at 2pm GMT, effectively seizing control of maritime traffic through the Strait of Hormuz — the narrow waterway between the Persian Gulf and the Gulf of Oman through which roughly one fifth of the world's oil supply passes. President Donald Trump, speaking to reporters on Sunday, made clear he was unconcerned about the breakdown in talks. "I don't care if they come back or not," he said. "If they don't come back, I'm fine."

Iran responded defiantly. An Iranian Armed Forces spokesperson declared that US restrictions on vessels in international waters were illegal and "amounts to piracy", and warned that the Islamic Republic would implement a "permanent mechanism" to control the strait. Iran's Revolutionary Guards separately cautioned that any approaching military vessels would be considered a violation of an existing ceasefire. Tehran's threats extended beyond its own coastline: the Iranian military warned that "no port in the region will be safe" if Iranian ports were endangered — a signal directed at Gulf states including the UAE and Oman. Iran's parliamentary speaker Mohammad Bagher Ghalibaf taunted Trump on social media, predicting Americans would soon be "nostalgic for $4–$5 gas."

Global markets responded sharply to the announcement. Brent crude — the international oil benchmark — surged above $100 a barrel for the first time in months, rising roughly 8% on the day, while US crude climbed a similar amount to around $104 a barrel. European stock markets opened in the red, with Spain's IBEX 35 falling 1.2% and Germany's DAX shedding 1.25%. Asian markets also declined, with Hong Kong's Hang Seng index dropping 1.2%. Shipping intelligence firm Lloyd's List reported that all traffic through the strait halted almost immediately after Trump's announcement, with vessels already transiting turning back.

Allied governments distanced themselves from the move. UK Prime Minister Keir Starmer was unequivocal, telling BBC radio that Britain "is not supporting the blockade" and would not be drawn into the conflict, despite Washington's earlier suggestions that London was sending minesweepers to assist. Starmer said British diplomatic efforts were focused entirely on reopening the strait to free navigation in order to stabilise energy prices for consumers. China's Foreign Ministry urged both sides to "avoid reigniting war" and called reports of Chinese weapons supplies to Iran "baseless smears." Australia also called for a swift return to negotiations and the full reopening of the waterway.

The human and economic toll of the wider conflict is already significant. The UN Development Programme warned in a new report that more than 32 million people worldwide could be pushed into poverty by the war's combined shock to energy prices, food supply chains and global growth — with developing nations expected to bear the heaviest burden. The Wall Street Journal reported that the Trump administration is additionally weighing a resumption of limited military strikes inside Iran. Trump himself reiterated threats to destroy Iranian civilian energy infrastructure if no deal is reached. With diplomatic channels now effectively severed and a naval confrontation taking shape in one of the world's most critical chokepoints, the prospects for a swift resolution appear remote.