TEHRAN: Iran's six presidential hopefuls were engaged in last-ditch campaigning Wednesday, hoping to woo the millions of Iranians still undecided between a slew of conservatives and a moderate cleric backed by reformists two days before the vote. Momentum has built for cleric Hassan Rowhani, a former top nuclear negotiator, after the withdrawal of reformist Mohammad Reza Aref on Tuesday, and the endorsement of two ex-presidents, pro-reform Mohammad Khatami and pragmatist Akbar Hashemi Rafsanjani.

Rowhani, 64, faces stiff competition from the conservatives, in particular hardline top nuclear negotiator Saeed Jalili and Tehran mayor Mohammad Baqer Qalibaf.

According to an opinion poll published by the Mehr news agency, Qalibaf is leading the race with 17.8 percent support from the 10,000 voters canvassed, ahead of Rowhani with 14.6 percent. They were followed by Jalili with 9.8 percent.

The number of undecided voters stood at 30.5 percent -- about 15 million voters -- while 11.3 percent declined to answer.