PORTLAND — State and federal regulators are asking for more data and analysis on water quality impacts of a liquefied natural gas terminal proposed on the Columbia River before they can decide whether it meets clean water and endangered species standards.

Those requests have been detailed in a recent letter from the Oregon Department of Environmental Quality and the National Marine Fisheries Service to the project's backers, Houston-based NorthernStar Natural Gas Inc.

The state agency has told NorthernStar that the additional studies could significantly delay what already has been a four-year regulatory process.

NorthernStar says it's premature to determine what, if any, delay would result from the additional data requests.

NorthernStar wants to build a $650 million LNG terminal 20 miles east of Astoria on an old mill site known as Bradwood.