The panel reviewing the proposed Mackenzie gas project says it needs more time before it can finalize its hearing schedule.

The joint review panel, which is looking at the environmental and social impacts of the $16.2-billion project, has been criticized for taking much longer to do its job than originally anticipated.

Now the panel says it wants to hear what the project's interveners have to say about a motion filed last week by the Sierra Club and the World Wildlife Fund before finalizing its schedule.

The two environmental groups want the panel to look beyond the pipeline project and study the cumulative effects of gas development in the Mackenzie Valley.

The panel has faced other setbacks, including a Federal Court ruling that said the northern Alberta First Nations should be part of the review.

Imperial Oil is the lead proponent of the proposed project, which also includes Exxon Mobil, ConocoPhillips, Shell Canada and the Aboriginal Pipeline Group.

The 1,200-kilometre pipeline is planned to deliver natural gas from three fields in the Beaufort Delta down the Mackenzie Valley to markets in the south.

The panel's next hearing is in Inuvik from July 9 - 11.

Once the hearings are completed, the seven-member panel has to comb through thousands of pages of evidence and hearing transcripts before writing its report.