Three conservation groups are suing the Department of the Interior for failing to meet a deadline on a decision to list polar bears as threatened because of the loss of Arctic sea ice.

The Center for Biological Diversity, the Natural Resources Defense Council and Greenpeace sued Monday in federal court in San Francisco. The groups say sea ice loss due to global warming is worsening.

The U.S. Fish and Wildlife Service proposed listing the animals as threatened under the Endangered Species Act. A decision was due on Jan. 9, but two months later, there's still no final word.