The eight men vying to become Iran's next president are set to face off in the first of three televised debates.
Friday's debate will be the first chance for the Iranian public to see the eight men on the same stage since campaigning began last week. So far, the candidates' public appearances have been limited to brief campaign stops and some short appearances on television and radio.
On Wednesday, Iran's Supreme Leader Ayatollah Ali Khamenei warned all the candidates to be truthful and respectful during the debates.
According to remarks published on his website, he said the candidates "should refrain from tarnishing their opponents and the realities of the society just to attract votes."
Four years ago, televised debates between Iranian President Mahmoud Ahmadinejad and pro-reform opponents Mir Hossein Mousavi and Mehdi Karroubi produced several heated exchanges.
Some candidates have already complained of censorship by authorities.
Mohammad Reza Aref, a former vice president seen by some analysts as the leading reformist candidate, had part of a speech airing on state-run television cut off.
Mohsen Rezaei, who served as commander of Iran's Revolutionary Guards, complained that parts of his first campaign-related interview on state-run television had been censored.
The first debate is expected to focus on Iran's struggling economy.
Recent government data show the unemployment rate is up to 13.1 percent. Inflation is at 12.1 percent with some economists predicting it could rise to about 30 percent.
Iran has endured several rounds of sanctions imposed by the international community over Tehran's failure to comply with curbs on its nuclear program. Analysts say the sanctions have greatly reduced Iran's crude oil exports, costing the country billions of dollars in revenue.