A Nebraska nonprofit on Friday said it will propose that Warren Buffett’s Berkshire Hathaway Inc. sell its investments in oil refiner Phillips 66 and other companies involved in fossil fuels over 12 years.

The Nebraska Peace Foundation, which focuses on anti-war, civil rights and environmental issues, said it submitted a formal proposal for Berkshire shareholders to consider at the Omaha-based conglomerate’s annual meeting next May 6.

Berkshire did not immediately respond to requests for comment on the proposal, which was reported earlier by the Associated Press.

The nonprofit would face an uphill battle absent support from Buffett, who commands nearly one-third of Berkshire’s voting power.

In April, shareholders including Buffett defeated its proposal that Berkshire report on the risks that climate change posed for its insurance businesses.

Buffett called that proposal unnecessary, and only 11 percent of the votes cast favored it.

The nonprofit said its fossil fuels proposal reflects the need to reduce greenhouse gases and shift toward renewable energy, without endangering Berkshire’s near-term profitability.

It said the proposal would not cover businesses that Berkshire owns outright, including several utilities and the chemical company Lubrizol.

Instead, it would cover investments such as Berkshire’s nearly $7 billion stake in Phillips 66, and its recently sold stake in Canada’s Suncor Energy Inc.

Buffett owns about 18 percent of Berkshire. Forbes magazine on Friday estimated his net worth at $71.7 billion.

The Suncor sale “reinforces our faith about what Warren Buffett can do about this,” Tim Rinne, state coordinator for Nebraskans for Peace, with which the foundation is affiliated, said in an interview.

“He’s a huge philanthropist, he’s an international icon and he’s extraordinarily smart,” Rinne said. “That puts him in an ideal position to make a statement for the entire world about addressing the perils of climate change.”

Berkshire owns more than 90 businesses including GEICO auto insurer, Dairy Queen ice cream and Fruit of the Loom underwear.

(Reporting by Jonathan Stempel in New York; Editing by Marguerita Choy)