Sirius has been looking for a loan since 2016 and now says it has received a conditional proposal from an unnamed major global financial institution.

In September last year, it upped the capital costs estimate for the project to $4.2 billion, up from the $3.7 billion forecast in November 2016, and revised the stage two capital funding requirements to an estimated $3.2-3.6 billion, $400-600 million higher than previous estimates.

In January, it said it had made progress towards obtaining commitments from lenders and adjusted the financing requirements to focus on a $3 billion three-tranche structure. 

It said at the time the first tranche would be an uncovered debt capital markets tranche, the second a commercial bank tranche, and the third an infrastructure and projects authority-guaranteed bond tranche.

However, these talks are on hold as Sirius said this plan could be replaced by the new proposal's alternative senior debt structure.

"The company believes that the alternative proposal potentially offers a more flexible and attractive solution to its stage two financing requirements and therefore it is pausing discussions with its existing prospective lenders to pursue the alternative proposal," Sirius said.

It was, however, progressing a number of options for the additional non-senior debt financing requirement outlined in September.

Sirius said it was working towards obtaining firm commitments for the alternative proposal and its additional financing requirements before the end of April, with the financial institution carrying out due diligence and internal approvals.

The company's shares jumped 8% Tuesday after the news to 19.39p (US25.17c), although the level was 28.8% lower than siz months ago.