SEATTLE (AP) — Saying there's a huge opportunity to move forward on climate change, The Nature Conservancy is weighing a potential carbon-tax ballot measure to put before voters as early as next year.

The Seattle-based conservation group on Monday filed three proposed initiatives to the people with the Secretary of State's Office as it prepares the groundwork for a possible 2018 ballot measure.

Mo McBroom, the group's government relations director, said the group is in the early stages of research and planning. They'll decide later this year or next year how to move forward with the boldest plan possible "at the soonest possible date," she said Tuesday.

"We are working to bring together the right set of interests, the right policy combinations that work for Washington, our communities, our business and establishing the political foundation for moving forward in the boldest way," McBroom said.

The proposed initiatives aim to reduce greenhouse gas emissions by charging a carbon tax or by giving the state authority to impose carbon fees on polluters. Money raised would go toward clean energy, clean water or other projects.

Last fall, Washington voters rejected a carbon-tax ballot measure that many business groups as well as major environmental and labor groups opposed. The Nature Conservancy did not take a position on Initiative 732.

In 2015, a coalition of diverse labor and environmental groups also announced plans for a carbon-tax initiative effort but didn't do so after I-732 qualified for the November 2016 ballot.

Follow the defeat of I-732, several lawmakers including Gov. Jay Inslee his year have proposed a carbon tax ranging from $15 to $25 per metric ton to raise money for various programs. Those proposals have gained little traction as the Legislature winds down its second special legislative session. A third overtime session appears likely.

The Republican-controlled Senate has been resistant to the idea. Critics have said a carbon tax would drive up fuel and energy costs and put Washington companies at a competitive disadvantage.

McBroom said if the Legislature does not act, it won't be the end of the conversation.

"We've made a major financial commitment to do all the work that needs to be done," she added, including gathering about 350,000 signatures to ensure the needed valid signatures.

"The people of Washington have made clear that they want to lead" on climate change, she said.