Iran's supreme leader Ayatollah Ali Khamenei has warned that any attack on his country would spark a regional conflict, as the US continues to build up its forces nearby, BBC reported. 

"The Americans should know that if they start a war, this time it will be a regional war," Khamenei was quoted as saying by the semi-official Tasnim news agency.

Donald Trump earlier said Iran was in "serious discussions" and he hoped they would lead to something "acceptable", while Iran's Foreign Minister Abbas Araghchi told CNN he was "confident that we can achieve a deal" on Tehran's nuclear programme, according to BBC.