SYDNEY, AUSTRALIA - A second attempt to plug a massive oil spill leaking from a rig off Australia's northwest failed Tuesday, but the operator said it hoped to try again within days.

Up to 400 barrels of oil have been pumped into the Timor Sea each day since the West Atlas drilling rig began leaking on August 21, forcing the evacuation of 69 workers, according to Bangkok-headed PTTEP Australasia.

The company failed in its first attempt last week to fix the leak at the Montara well-head platform, some 250 kilometres off the Australian coast.

PTTEP Australasia director Jose Martins said the second failure was disappointing but that each attempt improved the chances of success.

"Our drilling experts are hopeful that we will not need such a long side track to hit it on the next pass," Martins said.

He said the company was hoping to make its next attempt to plug the leak this weekend.

PTTEP is drilling a relief well some 2.6 kilometres under the seabed to divert the leaking oil and gas. Heavy mud will be used to plug the leaking bore.

The spill is reportedly Australia's worst since offshore drilling began more than 40 years ago, and ecologists fear the toxic cocktail of oil and dispersant chemicals could threaten marine and coastal species.