The Department of the Interior says it needs at least 10 more weeks to decide whether polar bears should be listed as threatened or endangered.

Assistant Secretary Lyle Laverty replied Thursday to a lawsuit filed by three conservation groups. He says the proposed listing raises “significant and complex factual and legal issues.”

A decision had been due Jan. 9.

Conservation groups petitioned to list polar bears as threatened more than three years ago because many scientists say their habitat, sea ice, is shrinking from global warming.

Kassie Siegel, spokeswoman for the Center for Biological Diversity, says the request for more time should be rejected. She says the law requires a decision by scientists, not attorneys.