Iran is preparing a counter-proposal after rejecting the U.S. nuclear deal, prompting President Trump to caution that "time is running out."

Trump said after a phone call with Putin on Wednesday that time was running out for Iran to make a decision on its nuclear programme and that he believed Putin agreed that the Islamic Republic should not have nuclear weapons.

The future of high-stakes negotiations over Iran's nuclear program remains shrouded in uncertainty as the U.S. and Iran publicly clash over the terms of an interim agreement proposed by the Trump administration that is intended to pave the way for a longer-lasting deal.