Gina Rinehart's Roy Hill joint venture faces a pivotal 48 hours, with export credit agencies in the US and Korea on the verge of approving billions of dollars of loans to the massive iron ore project.
The Roy Hill decision is top of the agenda for Thursday night's meeting of the board of the Export Import Bank of the United States, which has previously indicated preliminary support for $US694 million ($774 million) of finance for Roy Hill.
There have also been unconfirmed reports out of Asia that the Korea Exim Bank has approved $US1 billion of finance, with final decisions from similar agencies in Japan expected to flow within days.
Roy Hill, expected to cost close to $US10 billion, is a joint venture between Ms Rinehart's Hancock Prospecting, Korean steel giant POSCO, Japan's Marubeni and China Steel Corporation.
Despite renewed speculation in Asia that the project could cost more, the partners are still expecting to raise close to $US7 billion for the mine, port and rail project, with $US4 billion from export credit agencies, and close to $US3 billion from commercial banks such as ANZ and NAB.
A spokeswoman for the US Exim Bank told Fairfax Media that Thursday's meeting would involve the "final vote" on whether to fund Roy Hill, which has been open for review by US Congress for the past month.
The spokeswoman said the bank had received "a number of communications from members of Congress" on the Roy Hill decision this year, and had spent the past month taking further comment.
It was reported earlier this year that American iron ore miners were unhappy with the prospect of a foreign producer winning help from US taxpayers.
But those concerns were contested by representatives of states such as Wisconsin, where significant numbers of Caterpillar employees live.
Caterpillar plans to supply trucks to Roy Hill, just as it has already done for Fortescue, in the Pilbara.
Approval of the Roy Hill deal would add to the US Exim Bank's $US4.69 billion of exposure to Australian projects, with at least two of the big Gladstone LNG projects previously winning funding.
Airline Virgin Australia has also won funding in the past, on the grounds that it buys aircraft from US manufacturer Boeing.
According to its recent annual report, the US Exim authorised $US298.3 million of loans, guarantees and insurance to Australian projects in fiscal 2013.
While approval from the US would be a symbolic and very public win for Roy Hill, it is not considered the most influential lender to the project, with Asian banks dominating negotiations.
The US meeting is expected to get under way in Washington shortly after midnight Australian time.