Iran insisted it has no plan to attend a new round of negotiations with the United States on Monday, as uncertainty grows over a push to stop the Middle East war from resuming.

US President Donald Trump said he was sending negotiators to Pakistan for talks on ending the war that engulfed the region and rattled global markets, while repeating threats to attack Iran’s energy infrastructure if it did not make a deal.

After initial talks ended without a deal in Islamabad earlier this month, both sides have traded accusations of ceasefire violations, including the US seizure of an Iranian cargo ship early Monday that Trump said was trying to evade a US blockade of the country’s ports.