"In spite of protections already in place, Cook Inlet beluga whales are not recovering," said James Balsiger, acting assistant administrator of the National Oceanic and Atmospheric Administration.
The findings by NOAA's National Marines Fisheries Service conflict with claims by Alaska Gov. Sarah Palin, who has questioned scientific evidence that the beluga whale population in the waters near Anchorage continues to decline.
Palin, Republican presidential nominee John McCain's running mate, has strongly objected to the federal government's possible declaration of the whale as endangered.
It's the second run-in Palin has had with the Bush administration over the Endangered Species Act. She has.
The Cook Inlet beluga is one of five beluga whale populations in Alaska waters but the only one considered endangered.
NOAA said Friday the Cook Inlet population declined by 50 percent between 1994 and 1998 and "is still not recovering" despite restrictions on the number of whales that Alaska's native population can kill for subsistence.
It said that recovery of the beluga whale has been hindered by development and a range of economic and industrial activities including those related to oil and gas exploration in the Cook Inlet, which lies between the Alaska and Kenai peninsulas.
The Interior Department has proposed making available oil leases in the Cook Inlet as early as next year and in 2011, saying the waters have an estimated $1.38 billion worth of energy resources. Protection of the whale could hinder some of those activities.
The National Marine Fisheries Service "will identify habitat essential for the conservation of the Cook Inlet belugas in a separate rule-making within a year," said NOAA in a statement Friday.
The agency said NOAA scientists have estimated that the whale population in the inlet at 375 both last year and in another survey earlier this year, compared with a high of 653 belugas in 1995.
Other beluga populations off Alaska inhabit Bristol Bay, the eastern Bering Sea, the eastern Chukchi Sea, and the Beaufort Sea.