Legislative leaders planned to try to override Gov. Kathleen Sebelius’ veto of a bill allowing two coal-fired power plants in southwest Kansas after she rejected an alternative proposal Wednesday.

Sunflower Electric Power Corp. wants to build the plants outside Holcomb, in Finney County. The project has been blocked by Sebelius’ secretary of health and environment over their potential carbon dioxide emissions, because many scientists link such man-made greenhouse gases to global warming.

“What keeps coming back is minor variations of the original proposal,” Sebelius said during a news conference. “This doesn’t get us very far down the road.”

Sebelius has vetoed two bills to clear the way for the plants and reduce the secretary of health and environment’s power. Top legislators offered her an alternative that would make the two plants 14 percent smaller than originally proposed.

The Democratic governor called the Republican leaders’ plan an ultimatum because they said they would try to override her last veto if she rejected it. She met with the leaders Wednesday morning, then held her news conference an hour before lawmakers reconvened after their annual spring break.

The governor has suggested allowing one plant, if Sunflower would commit to investing in new wind farms and starting programs that help its consumers conserve power. The utility rejected her plan, saying it’s unworkable.

Sunflower and its allies need two-thirds majorities in both chambers to override a veto. They’ve always had more than enough votes in the Senate, but they’ve remained at least one vote short in the House.

“We’ll proceed. We have our work to do,” said House Speaker Melvin Neufeld, an Ingalls Republican who strongly supports Sunflower’s project. “We’ll do it.”

Last week, Lt. Gov. Mark Parkinson, the governor’s top adviser on energy issues, told reporters the administration was considering options to continue blocking Sunflower’s project even if legislators overrode Sebelius’ veto. He wasn’t more specific.

Sebelius said the only option her administration has discussed is the prospect of a third party - such as environmentalists - filing a lawsuit if legislators override the governor’s veto. Sebelius views a lawsuit as likely but said her administration would not be part of it.

Anticipating legislative action, supporters and opponents came to the Statehouse to lobby. Dozens of opponents gathered outside the House, briefly forcing members to walk between them to get to the chamber.

“We need to start factoring in concerns about climate change into decisions about our energy,” said opponent Brian Sifton, a University of Kansas senior from Kansas City, Mo.

But pipe fitters Kirk Miller, of Havensville, and Mike Wolownik, of Frontenac, came to show support for Sunflower’s project because of its potential to create jobs. They said they’re concerned about CO2 but that Sunflower’s plants would use technology making them perhaps the cleanest in the nation.

“My grandparents came to this country to mine coal. My father was a railroader to move coal,” Wolownik said. “Now I build them.”

Sunflower estimates the cost for building two, 700-megawatt plants outside Holcomb at $3.6 billion, but critics believe it could exceed $5 billion because of rising construction costs.

The new generating capacity, 1,400 megawatts, would be enough to meet the peak demands of 700,000 households, according to one state estimate. Of that, 1,200 megawatts would go to Hays-based Sunflower’s two out-of-state partners - Tri-State Generation and Transmission Association Inc. of Westminster, Colo., and Golden Spread Electric Cooperative, in Amarillo, Texas - which would help finance the plants.

The latest proposal from Neufeld and Senate President Steve Morris, a Hugoton Republican, proposed allowing Sunflower to build two, 600-megawatt plants. That would reduce the generating capacity reserved to Tri-State and Golden Spread to 1,000 megawatts.

Sebelius said the remaining 200 megawatts of power for Sunflower and Midwest Energy wouldn’t be enough to meet even western Kansas’ needs.

She suggested a single coal-fired plant, dedicated to Kansas customers. However, she acknowledged Sunflower probably couldn’t finance such a project on its own.

Earl Watkins Jr., Sunflower’s chief executive officer, said his company doesn’t intend to abandon its partners.

He said Sebelius’ proposal “doesn’t meet our members’ needs or the participants who have been working with us all this time.”