Manuel Balce Ceneta/Associated Press

The nation’s top energy regulator on Monday formally accused JPMorgan Chase of manipulating energy markets, foreshadowing a multimillion-dollar settlement that is expected as early as this week, according to people briefed on the matter.

The action by the Federal Energy Regulatory Commission is largely a formality ahead of the settlement — a deal that is expected to help JPMorgan avert a clash over accusations that the bank orchestrated trading strategies to turn inefficient power plants into profit centers, the people said.

From the outset, JPMorgan, which declined to comment on Monday, has denied any wrongdoing. The bank has also mounted a fierce defense of the top executives who supervised the traders in Houston accused of devising the trading strategies.

The accusations against JPMorgan stem from its rights to sell electricity from power plants. The rights come from assets that the bank acquired in the 2008 takeover of Bear Stearns.

To transform the power plants into profit generators, the agency contends, JPMorgan’s traders adopted eight different “schemes” from September 2010 to June 2011. Under the plan, the traders offered the electricity at prices that appeared falsely attractive to state energy authorities. The effort prompted authorities in California and Michigan to make excessive payments that helped drive up energy prices, the regulator said.

The settlement could cost the bank as much as $500 million, people briefed on the matter said. Accusations of market manipulation surfaced this spring in a confidential commission document, reviewed by The New York Times, which outlined a pattern of illegal trading in the electricity markets of California and Michigan. The document, a warning that investigators would recommend civil charges, also contended that a senior JPMorgan executive, Blythe Masters, gave “false and misleading statements” under oath. Ms. Masters, however, was not included in the regulator’s formal notice on Monday. JPMorgan denies that she made false statements under oath.

Initially, investigators planned to recommend that the agency hold Ms. Masters and three of her employees “individually liable.” The investigators backed away from that decision, the people briefed on the matter said.