US Secretary of State John Kerry said on Sunday world powers would pursue further talks with Iran to resolve a decade-old dispute over its nuclear programme, but stressed the process could not go on forever.

World powers and Iran failed again to bridge the gap at weekend talks in Kazakhstan, prolonging a stand-off that could yet spiral into a new Middle East war. No new talks were scheduled between Iran and the six powers.

"This is not an interminable process," said Kerry after arriving in Istanbul on Sunday on the first leg of a 10-day trip to the Middle East, Europe and Asia.

He said US President Barack Obama was committed to continuing the diplomatic process despite what he called the complicating factor of an Iranian presidential election in June.

"Diplomacy is a painful task... and a task for the patient," Kerry told a news conference.

Israeli Strategic Affairs Minister Yuval Steinitz urged the powers on Sunday to set a deadline of weeks for military action to persuade Iran to halt its nuclear enrichment activity. - Reuters