Ramin Mehmanparast, Iran's foreign ministry spokesman, welcomed Vakili Rad's expected return.
"To see him in Iran after years, we are pleased," he said.
However, controversy has raged in France over whether the decision to release Vakili Rad was tied to Iran's release of Clotile Reiss, a French academic.
Opposition Socialists have suggested that France secured the release of Reiss in exchange for sending Vakili Rad home along with a second man, Majid Kakavand, who is wanted in the US for trial.
But French officials have denied any dealmaking over Reiss, who was sentenced to 10 years in prison by Iran for allegedly spying during the post-election violence in the country last year.
Bernard Kouchner, the French foreign minister, insisted that there had been no "payoff" and no "horse-trading" between Paris and Tehran.
"We were never in a logic of the slightest bargaining," a ministry spokesman said.
Sorin Margulis, Vakili Rad's lawyer, also denied speculation of a deal, saying: "This must not be seen as an exchange. The Reiss affair did nothing but complicate and delay my client's release."
Convicted of murder
Vakili Rad was convicted in 1994 of murdering the 76-year-old Bakhtiar at his home on August 6, 1991. He served his jail term in Poissy, west of Paris.
The last prime minister under Shah Mohammad Reza Pahlavi, Bakhtiar fled to France in 1980 after the Islamic revolution. His home in Suresnes, west of Paris, had been under round-the-clock police surveillance.
Vakili Rad and an accomplice were allowed inside the villa by an aide to Bakhtiar, who was murdered along with Fouroush Katibeh, his secretary.
Arrested in Switzerland, he was extradited to face trial in France but the other two accomplices escaped.
A French appeals court ruled on July 2 last year that Vakili Rad could be given conditional freedom, but the decision was delayed twice.
French law allows expulsion for foreigners with no ties to France once they are released.
The French prosecutor's office said Tuesday that it was able to order Vakili Rad's release because he had requested that he be sent back to Iran if he were freed.
The only issues that could delay a Tuesday departure are whether Vakili Rad has received an up-to-date passport and whether formalities are concluded
in time to catch a flight home.