"We do not know exactly when the end will come and the guidelines should be observed for a long period," Rouhnai told a meeting of the National Headquarters for Managing and Fighting the coronavirus in Tehran on Saturday.
"People should know that the epidemic will take long and today we are not in possession of a definite and clear end to the epidemic," he added. "We may have a long period ahead until we can have access to an approved and available vaccine."
The president noted that the country has no choice but to open factories and shops while simultaneously countering the highly contagious virus.
He further advised Iranians to observe health and safety norms, respect social distancing rules, use masks at gatherings and avoid wedding ceremonies or funeral processions.
Like many other countries, Iran is grappling with the coronavirus that first showed up in China in late December 2019 before spreading across the globe.
Over 167,000 Iranians have contracted the disease and 8,134 have died while more than 129,700 patients have recovered so far, according the latest figures released by the Health Ministry.