Iran has rejected a US offer to supply it with medical isotopes if it stops further enriching uranium. A foreign ministry spokesman said in Tehran that the offer is not logical as shutting down their reactor or stopping the production of medicine is not the solution.Meanwhile, Washington has extended its sanctions against Iran by taking further action against the Revolutationary Guards and four other affiliated construction companies. The US Treasury said Revolutionary guard's growing presence in Iran's financial, commercial, defence, construction and oil sectors meant profits were available to support illicit activities.