ROME - U.S. and Israeli officials differed over Iran's nuclear programme on Wednesday as Israel called for its effective dismantlement and the United States suggested safeguards could show that it is peaceful rather than military.

U.S. Secretary of State John Kerry and Israeli Prime Minister Benjamin Netanyahu spoke as they began talks ostensibly about Israeli-Palestinian peace negotiations but which appeared likely to be overshadowed by Iran.

"Iran must not have a nuclear weapons capability, which means that they shouldn't have centrifuges (for) enrichment, they shouldn't have a plutonium heavy-water plant, which is used only for nuclear weapons," Netanyahu told reporters.

"They should get rid of (their amassed) fissile material, and they shouldn't have underground nuclear facilities, (which are) underground for one reason - for military purposes." He called Iran's programme the region's foremost security problem.

Iran says it is enriching uranium solely for electricity and medical treatments, not nuclear weapons.

Kerry, whose aides are exploring a diplomatic solution to rein in Iranian nuclear activity, took a tack different from Netanyahu by suggesting Iran could show its programme was peaceful by adhering to international standards followed by other nations.

"We will pursue a diplomatic initiative but with eyes wide open, aware that it will be vital for Iran to live up to the standards that other nations that have nuclear programs live up to as they prove that those programmes are indeed peaceful," Kerry said as he and Netanyahu began a meeting at the U.S. ambassador's residence in Rome.