The question of whether Vermont's only nuclear plant can continue operating without the approval of state regulators goes before a federal appeals court Monday in a dispute that has gained increasing attention nationally about the boundaries of federal authority over a controversial power source.

The New Orleans-based Entergy Nuclear Operations Inc. brought the issue to court. The utility won a decision last January in which a federal judge in Brattleboro, Vt., ruled that safety issues are the sole responsibility of the federal Nuclear Regulatory Commission. In 2011, that panel had extended the license for Entergy's Vermont Yankee plant by 20 years. Without the judge's ruling, the plant could have been forced to close on March 21, when state approval expires.

The 2nd U.S. Circuit Court of Appeals in Manhattan took up the case on an expedited schedule, and a ruling from the three-judge panel that will hear arguments Monday could be expected within weeks rather than months.

At stake is a plant that opened in 1972 and supplies one-third of the electricity consumed by Vermont, with about 45 percent of the power generated at the plant being shipped to electric companies in neighboring states.

In written arguments submitted before Monday's hearing, lawyers for Vermont officials said that even the NRC acknowledged when it relicensed the plant that state regulators will "ultimately decide" whether the plant continues to operate. The lawyers noted that the dispute originates in a state that has become "a national leader in promoting energy efficiency" as it has for decades engaged in moves away from oil, gas and nuclear to such renewable energy sources as solar, wind and biomass.