The financing comprising a US$400 million equity fundraising, convertible bonds of $644 million, senior secured guaranteed bonds of $500 million, and a committed and secured revolving credit facility of maximum $2.5 billion.

CEO Chris Fraser said the company's March discussions with prospective lenders for alternative financing had resulted in this "comprehensive markets-led solution for our funding requirements which will enable Sirius Minerals to complete the development of its mine and unlock what we believe to be the world's largest known high-grade polyhalite deposit". 

He said the funding package combined equity, convertible bonds, high yield debt, and a $2.5 billion revolving credit facility in a multi-stage, flexible structure that balanced the availability of capital with the needs of the project. 

"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," he said.

The equity fundraising was launched immediately after the announcement at a price between 15p (US19.5c) and 18p per new ordinary share, with around 90% expected to be sold to institutional investors.

Sirius' shares (AIM:SXX) were trading at 18.03p Tuesday, down 17.67%. 

The guaranteed convertible bonds were launched at the same time, with a principal amount of $200,000. 

The bonds will be convertible into fully paid ordinary shares of Sirius with the initial conversion price expected at a premium of 20-25% above the share clearing price in the concurrent equity placement.

Sirius said up to $244 million of the convertible bonds would likely be used to buy an equivalent amount of Sirius' existing 8.5% guaranteed convertible bonds due 2023 through the newly launched buyback, meaning $400 million of the new convertible bond offering was fully underwritten at launch.

Through the book-building process, or convertible bonds buyback, launched simultaneously with the financing package, Sirius said it intended to purchase any and all existing convertible bonds from holders using funds from the proceeds of the convertible bond offering.

It expects the buyback to close in May.

Sirius said the revolving credit facility with JP Morgan was contingent on the completion of the full $500 million senior secured guaranteed bond issue before the end of October.

The company said it expects the initial drawdown under the credit facility to take place no later than June 2021.