Oil prices surged and stocks sank Monday after US-Iran peace talks fell apart and Donald Trump announced a blockade of the strategic Strait of Hormuz, adding to fears of energy supplies from the Middle East.
Negotiations in Islamabad at the weekend fell apart with the US delegation -- led by Vice President JD Vance -- blaming Iran's refusal to give up its nuclear program and Tehran hitting out at "maximalism, shifting goalposts, and blockade".
The news dealt a blow to hopes for an end to the six-week conflict, which has sent crude prices soaring, pushing inflation up and sending shivers through the global economy, said AFP.
Oil prices -- which tumbled last week after the United States and Iran agreed to a ceasefire -- jumped around eight percent Monday, with both contracts topping $100 a barrel.
Equities fell across Asia, with Tokyo, Hong Kong and Seoul off at least one percent, while Shanghai, Sydney, Singapore, Taipei and Jakarta were also down.
In a lengthy social media post, US President Donald Trump said his goal was to clear the strait of mines and reopen it to all shipping.
But he said that Iran must not be allowed to profit from controlling the waterway -- through which a fifth of global oil and gas usually passes.
"Effective immediately, the United States Navy, the Finest in the World, will begin the process of BLOCKADING any and all Ships trying to enter, or leave, the Strait of Hormuz," Trump wrote on Truth Social.
"Any Iranian who fires at us, or at peaceful vessels, will be BLOWN TO HELL!"
He said the blockade would only apply to vessels travelling to or from Iranian ports.
The US military said Sunday it will blockade all Iranian Gulf ports on Monday at 1400 GMT, effectively seizing control of maritime traffic.
Iran's Revolutionary Guards said its security forces had full control over the strait and warned enemies would be trapped in a "deadly vortex" in case of any "wrong move".
Iran's navy chief Shahram Irani called Trump's threat "ridiculous and funny", according to state TV.
After the talks -- the highest-level meeting between the two sides since the 1979 Iranian revolution -- Vance said Washington had made Tehran its "final and best offer," adding: "We'll see if the Iranians accept it."
Iran's Foreign Minister Abbas Araghchi said the rivals had been "inches away" from a deal, writing on X that "Iran engaged with US in good faith to end war".
But he added "we encountered maximalism, shifting goalposts, and blockade".
Nicole Grajewski, an assistant professor at the Center for International Research at Sciences Po in Paris, warned that a US blockade was "not a minor coercive signal" but would rather be considered an effective resumption of the war.
Fawad Razaqzada, a market analyst at Forex.com, said: "The fundamental issue remains trust - or rather, the lack of it - between two long-standing adversaries who still appear some distance from common ground."
Investors are also keeping an eye on attempts to resolve the conflict between Israel and Hezbollah, as Lebanese Prime Minister Nawaf Salam said he was pushing to ensure the withdrawal of Israeli forces.
"We will continue to work to stop this war, to ensure the Israeli withdrawal from all our lands, the return of all the prisoners, to rebuild our destroyed villages and towns, and the safe return of the displaced," Salam said.
The prospect of the Middle East crisis continuing for the foreseeable future ramped up inflation fears and weighed on gold amid expectations interest rates would be kept elevated.
Data Friday highlighted the impact of the conflict on prices, with the US consumer price index spiking at 3.3 percent in March, its highest since May last year.
