Puget Sound Energy has canceled the sale of Colstrip Unit 4 shares to NorthWestern Energy and Talen Energy.

The Seattle-area utility called off the sale Thursday, according to a press release quoting Ron Roberts, the utility’s director of generation and natural gas storage.

“Unfortunately, the proposed transaction has hit roadblocks that significantly undermine the prospects for successful completion of the transaction,” Roberts said. “While we are deeply disappointed by this development, we remain committed to finding ways to quickly and efficiently remove coal from our portfolio in compliance with our state’s mandate to have a coal-free energy supply by 2025.”

The largest stakeholder in Colstrip Power Plant, Puget announced last December that it had agreed to sell its 25% share of Unit 4 to NorthWestern Energy. A few months later, power plant operator and stakeholder Talen Energy announced that it wanted half of what Puget was selling, which it had first right of refusal to buy.

There were conflicts among the buyers about whether Talen’s right-of-refusal also extended to a portion of Puget’s share of the Colstrip Transmission Line, a portion of which NorthWestern also intended to buy. Differences over the transmission were still unsettled last week when Puget asked its regulator, the Washington Utility and Transportation Commission, to reschedule proceedings while arbitration continued.

The WUTC investigative staff and the Washington Public Counsel had both advised against the sale, which they concluded was bad for Puget customers. The recommendations were that Puget move toward closing Colstrip, while also keep its transmission line ownership, which could be put to use importing Montana renewable energy.

Puget and two other Washington utilities face a 2025 ban on coal power under a state law addressing climate change.