Rio Tinto has reportedly understood to have just two weeks left before three quarters of the banks committed to funding its Mongolian Oyu Tolgoi project expansion hit expiry dates.

Fairfax Media believes 15 of Rio’s nearly 20 lenders, including Australia’s export credit agency, will hit a commitment expiry date on March 31.

Crucially, the $US1.4 billion commitment from the World Bank’s International Finance Corporation is not subject to an expiry date. Rio raised support of $US4.2bn from its syndicate so the IFC’s ongoing support is important.

But Fairfax understands the Australia”s Export Finance and Insurance Corporation isn’t open-ended. The EFIC was unable to comment on the story.

The $10bn copper-gold project has been subject to numerous delays due to disagreements with the Mongolian government.