The debt and equity deal will raise £2.9bn and guarantee the progress of infrastructure work at the giant site in Yorkshire.
Announcing the funding plan to the City, Sirius Managing Director and Chief Executive Officer Chris Fraser said: “Today’s announcement provides a clear pathway to a fully financed project in the months ahead, while enabling us to progress construction at full speed.”
The initial construction phase of the project is expected to see the first potash extracted from mines by 2021.
Construction is underway at all main sites for phase one with Austrian specialist Strabag on board for the three main 23-mile tunnel drives to transport excavated material to the coast.
McLaughlin & Harvey has also been chosen to develop a major port materials handling facility at Teesside.