Downer told reporters that all major differences between East Timor and Australia have been resolved including the contentious issue of unitisation of the Greater Sunrise gasfield.

While details of the agreement with East Timor are unknown, ratification of the treaty should pave the way for deals worth $20 billion to supply gas from the Bayu-Undan field to Japanese customers.

Operator of the field, ConocoPhillips, had earlier warned that Japanese customers wanted treaty ratification by 11 March or the project would fall through.

The Northern Territory's Chief Minister Clare Martin said once the treaty is ratified by the Australian Parliament, ConocoPhillips will be in a position to make the $3 billion investment in bringing gas from Bayu Undan into Darwin and building an LNG plant.