Pakistan, June 11 -- A fragile ceasefire between the United States and Iran appeared to be hanging by a thread on Wednesday after the two sides exchanged fresh military strikes; President Donald Trump warned Tehran it would "pay the price" for delaying a deal, and Iran said it had targeted US-linked military facilities across Jordan and the Gulf.

The sharp escalation, one of the most serious direct exchanges since the April truce, came less than 48 hours after Trump said negotiations with Iran were in their "final" stage and that an agreement could be possible within days.

The immediate trigger was the reported downing of a US AH-64 Apache helicopter near the Strait of Hormuz, one of the world's most sensitive energy corridors.

Preside...