Federal Environment Minister Greg Hunt has given himself more time to decide whether to allow a fourth gas plant to be built on Queensland's Curtis Island.
Mr Hunt was due to make a decision on the project on Wednesday but has pushed the deadline back to December 13.
A spokesman from his office said this would allow more time for "further consideration".
Earlier this year, UNESCO said Australia needed to rein in major Queensland coastal developments or risk having the reef listed as a World Heritage site "in danger".
Arrow Energy's plan to build an LNG plant on Curtis Island, off Gladstone, was given state approval in September.
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The LNG plant would have the capacity to process 18 million tonnes of gas each year once completed.
Environmental groups say the project shouldn't go ahead because it involves dredging about one million cubic metres of soil to give ships access the plant.
Australian Marine Conservation Society reef campaign spokeswoman Felicity Wishart says increased sediment in the water could hurt turtles, dugongs and damage coral.
"Curtis Island is within the reef's world heritage area yet its mangroves and beaches are being destroyed to build gas processing plants," she said.
Another green group, Save the Reef, has said the government has set out "vague" water quality testing requirements for the plant rather than sticking to national guidelines.
However, the Department of Development, Infrastructure and Planning says all Curtis Island developments must adhere to state and national guidelines.
