State television said the first turbine in the Rogun hydroelectric dam could come online in November, quoting Pietro Salini, chief executive of the Italian company Salini Impregilo that has been contracted to oversee the project.
Salini met with Rakhmon on Wednesday.
The November 16 launch date for the first unit coincides with a holiday honouring the 65-year-old Rakhmon, who has been president for nearly a quarter of a century and is the subject of a flourishing personality cult.
There have been calls by public figures in the country to rename the dam, planned to be 335 metres tall (1,099 feet) — which would make it the tallest hydroelectric dam in the world — after Rakhmon.
A former collective farm chief who consolidated control over Tajikistan following a five-year civil war that ended in 1997, Rakhmon jumped behind the wheel of a bulldozer to kickstart work on the project in 2016.
Plans to build a dam on the Vakhsh River in southern Tajikistan date back to the Soviet era, but the project was scaled up following the breakup of the Soviet Union.
Tajikistan regularly suffers power blackouts in winter. It also views the Rogun dam as an opportunity to export electricity across the region.
But the Italian company managing the project said it may be a decade before it reaches its full capacity of 3,600 megawatts.
Tajikistan is a key part of the US-backed CASA-1000 project that aims to increase supplies of electricity from the region to Afghanistan and Pakistan.