TEHERAN (AGENCE FRANCE-PRESSE) - Iran's top two presidential candidates launched a final day of election campaigning on Wednesday (May 17) as the country's supreme leader called for a massive turnout to bolster the regime against its "enemies".

Ayatollah Ali Khamenei suggested Iran's foes would be deterred from pursuing regime change if they saw voters flock to the ballot boxes in Friday's (May 19) poll.

"American, European officials and those of the Zionist regime are watching our elections to see the level of participation," he said in quotes carried on his Telegram messenger account.

"The Iranian nation has enemies. Faced with the enemy, the people should show its determination and calm," he said.

Turnout is all-important to the Iranian regime, which uses regular elections to demonstrate the legitimacy of its Islamic system.

But on the campaign trail, two starkly different visions of how that system will evolve have been on display.

President Hassan Rouhani, a 68-year-old moderate cleric, defended his international outreach, which included a nuclear deal with world powers that ended many sanctions in exchange for curbs to Iran's atomic programme.

Mr Rouhani told his hardline opponents they were not equipped to continue his diplomatic efforts.

"You say you want to negotiate with the world, but you don't know how to speak the global language. You don't even know how to speak the language of your own people," he said at a rally in the northern town of Ardebil.

His hardline opponent, 56-year-old cleric Ebrahim Raisi, has vowed to stick by the nuclear deal, but said the government had made too many concessions to the West and failed to "cash the cheque" offered by the accord.

"A diplomacy of supplication will not solve our problems. We need a diplomacy of strength," he told supporters in Teheran, according to ISNA news agency.

Mr Raisi said Iran's continued exclusion from international banking, despite the nuclear deal, was proof that Mr Rouhani's diplomacy had failed.

"Some people say that if we're elected, the sanctions will return," said Mr Raisi.

"But in what measure have the sanctions been lifted? The banking sanctions that were the most important are still in place."

Campaigning will draw to a close on Thursday (May 18) morning, 24 hours before polls open.

Mr Rouhani is still seen as the front-runner, though polling is unreliable in Iran.

Early election results are expected on Saturday (May 20).

The conservative-dominated Guardian Council selected six candidates to stand in the election, but two have dropped out, effectively creating a two-horse race between Mr Raisi and Mr Rouhani.

Conservative Mostafa Mirsalim and reformist Mostafa Hashemitaba are still in the race, though they are not expected to win more than a small share of the vote.