An Oklahoma-based energy association and the state of Oklahoma are suing the U.S. Fish and Wildlife Service over the agency's court settlement that could lead to adding the lesser prairie chicken to the endangered species list.

The lawsuit was filed Monday in U.S. District Court in Tulsa, Okla., by Domestic Energy Producers Alliance and Oklahoma Attorney General E. Scott Pruitt.

While the lawsuit asks for injunctive relief, there's no specific request to delay the perhaps imminent listing of the prairie chicken.

Under the terms of settlement agreement approved by a federal district judge, FWS must file its decision on the chicken no later than March 31.

The group also filed its notice of intent to sue for violations of the Endangered Species Act.

The Kansas Independent Oil and Gas Association is one of several state groups that are partners in the DEPA group, and Ed Cross, KIOGA's president, is a member of the executive committee of the group.

A spokesman for Kansas Attorney General Derek Schmidt said the agency is aware of the lawsuit.

"We are studying the legal issues involved and considering the potential options and effects on Kansas," communications director Clint Blaes said in an email.

DEPA's lawsuit essentially is challenging the federal agency's "use of sue-and-settle tactics to regulate behind closed doors."

The 47-page lawsuit, DEPA said in a statement, is in response "to two unprecedented secret settlements between the FWS and anti-development interest through which FWS voluntarily committed to complete hundreds of Endangered Species Act listing decisions within the span of only a few short years."

The lawsuit, however, takes particular aim at the lesser prairie chicken.

A decision on whether or not to list the lesser prairie chicken as threatened as FWS has proposed to do must be made by March 31.

An FWS spokeswoman wouldn't say when the decision will be made.

While DEPA suggests the settlements were secret, the agreement long has been public. That settlement, approved September 2011 with WildEarth Guardians and the Center for Biological Diversity requires FWS to issue listing decisions on 253 candidate species by the end of fiscal year 2016.

A three-judge appeals panel already has upheld the settlement, despite the objections of Safari Club International, its members specifically citing plans to continue hunting the New England cottontail, the greater sage grouse and the lesser prairie chicken.

The appeals court actually answered some of the issues raised in Monday's filing by DEPA and Oklahoma.

That issue deals with the settlement's mandate that FWS must determine the species listed are either warranted for listing or not warranted.

The lawsuit claims FWS has a third option, warranted but precluded because the species has a lower priority than other species.

"... The ESA does not require the service to find that listing a species is precluded under any specific circumstances," the appeals court ruled in its January 2013 ruling.

In announcing the filing, Oklahoma Attorney General Scott Pruitt slammed the "friendly settlements of lawsuits."

Pruitt went on to say Oklahoma and other states have spent $26 million to develop a voluntary and comprehensive conservation plan to protect the lesser prairie chicken.