DENVER (AP) — Democratic presidential candidate Michael Bennet said Monday he wants to commit $1 trillion for underwriting research and projects to address climate change, set aside about one-third of U.S. lands and ocean territory for conservation and reach net-zero U.S. emissions by midcentury.

His campaign's climate plan also would require utilities to offer consumers green-energy options as the Colorado senator joined two rivals for the 2020 nomination, former Texas Rep. Beto O'Rourke and Washington Gov. Jay Inslee, who already have released detailed proposals on the issue.

Bennet's timetable of net-zero emissions no later than 2050 is longer than some activists have called for, but he said it was realistic and in line with what scientists say is needed. In a nod toward a possible tighter time frame, Bennet said the federal government would fund a "climate challenge" and pay states that reduce emissions by 2030.

Bennet said he tried to design the plan so any subsequent Republican administrations could not easily overturn his actions.

"You cannot put in a set of policies for two years and have them ripped out for another two years," Bennet told reporters. "The most important thing we have to do is build a broad constituency to take on climate change."

To do that and protect against the GOP reversing his policies, Bennet focuses on agriculture by creating an agency to finance innovative projects intended to reduce greenhouse gas emissions and by increasing incentives for farmers to use zero-emission energy.