Sole reformist candidate Mohammad Reza Aref announced Tuesday he was pulling out of Iran's presidential election following calls for reformists to rally around moderate candidate Hassan Rowhani.
Aref said on his website that former reformist president Mohammad Khatami had sent him a letter advising that it "would not be wise" for him to remain as a candidate in Friday's vote.
Khatami's intervention came amid growing calls in recent days from within the reformist camp for Aref to quit in favour of Rowhani.
Khatami's advisory council in a statement said it was backing Rowhani as the "reformist camp candidate."
However, Aref did not declare his support for any other candidate in the statement announcing his withdrawal.
Rowhani was Iran's former top nuclear negotiator under Khatami and served as a top security official under the pragmatic former president Akbar Hashemi Rafsanjani, whose backing he still enjoys.
"I will follow the paths of Khatami and Rafsanjani," the media quoted Rowhani as saying on Monday at a rally in the western Iranian province of Kurdistan.
"I do not approve of the current foreign policy. We should try to have good (international) interactions to gradually reduce the sanctions and finally remove them," he added.
Rowhani has advocated a policy of flexibility in negotiations over Iran's controversial nuclear drive, which world powers believe is masking an atomic weapons programme despite repeated denials by Tehran.
While Rowhani was Iran's top nuclear negotiator, Tehran agreed to suspend uranium enrichment and to implement snap inspections by the UN atomic watchdog in accordance to the non-proliferation treaty.
Aref is the second of the eight candidates in the election to withdraw.
Ex-parliamentary speaker Gholam Ali Haddad Adel, seen as close to supreme leader Ayatollah Ali Khamenei, pulled out of the race on Monday, asserting, "promoting the chances of a conservative election."
Rowhani, a 64-year-old cleric will now face hardline conservative Saeed Jalili, former foreign minister Ali Akbar Velayati and Tehran's mayor Mohammad Baqer Qalibaf.
Hopefuls Mohsen Rezai and Mohammad Gharazi are trailing in the surveys ahead of the election.
Supporters of Jalili, the current head of the Supreme National Security Council, who is also tasked with negotiating with the world powers, has harshly criticised Rowhani's approach then, saying he made too many concessions in return for too little.
Rowhani quit his post in 2005 over disagreement with President Mahmoud Ahmadinejad. Iran resumed the sensitive uranium enrichment work which it "voluntarily" suspended and ceased to executed the snap inspection.
On Tuesday, Iranian pro-reformist and moderate newspapers hailed Aref's withdrawal.
The reformist Arman ran the headline "Aref greets Rowhani... the great consensus," while the Etemad newspaper ran its main story as: "Reformist votes Rowhani," adding that the decision follows weeks of deliberations.
The move by Aref has prompted the conservative camp to call for such union among the remaining conservative candidates.
"In case of division of the vote among the conservatives, then the conservative candidate will be elected with just a few more votes than his reformist rival," wrote the publisher of the hardline Kayhan newspaper, Hossein Shariatmadari.