President Donald Trump's threat comes as negotiations have stalled and sporadic attacks in the region have continued.
The United States launched fresh attacks against Iran on Thursday, prompting Tehran to retaliate, as US leaders accused their counterparts of dragging out negotiations for a deal to end the three-month war.
The second straight day of tit-for-tat strikes, with Iran targeting US bases across the Gulf, sent oil prices rising again.
US President Donald Trump, who had repeatedly said negotiations with Tehran were close to an end, said Wednesday that Iran keeps "playing us for suckers" and will now "have to pay the price".
Hours after, US Central Command (CENTCOM) said American forces began "additional self-defence strikes" at 5:15 pm on Wednesday Washington time – early Thursday in Iran – in response to what it called Tehran's "unwarranted and continued aggression".
