WASHINGTON — Sen. Bernie Sanders will speak at a Green New Deal rally at Howard University on Monday that also features Rep. Alexandria Ocasio-Cortez, organizers said.

The event, organized by the Sunrise Movement, gives the 2020 contender a high-profile platform to court the environmental left.

Sanders' planned appearance comes as Democratic candidates are starting to spar over their climate plans and recent polls show environmental issues taking on greater importance for Democratic voters than inprior elections.

Campaigns are still only beginning to roll out plans, but early splits have emerged over the Green New Deal, which calls for a rapid transition from carbon emissions associated with global warming by 2030, and the role fossil fuels should play in the transition.

On Thursday, both Sanders and Washington Gov. Jay Inslee criticized a reported plan by Joe Biden to seek a "middle ground" policy that would focus on advancing Obama-era regulations and potentially include a role for natural gas and coal.

"There is no 'middle ground' when it comes to climate policy," Sanders tweeted. "If we don't commit to fully transforming our energy system away from fossil fuels, we will doom future generations. Fighting climate change must be our priority, whether fossil fuel billionaires like it or not."

The Sunrise Movement, which warned Biden’s reported approach would be "a death sentence for our generation" in a statement, has so far set a high bar for candidates.

The group lavished praise on a plan by Inslee to set targets of making new vehicles and buildings zero-emission by 2030 and transitioning to clean electricity by 2035. But they delivered a mixed response to a plan by Beto O’Rourke last month to invest $1.5 trillion in green infrastructure and research, thanking him for pledging to make the issue as his top priority but criticizing him for setting a goal of achieving net-zero emissions by 2050 rather than 2030.

Experts have generally been skeptical a Green New Deal could achieve its goals within 10 years.

The speaking schedule for Monday's event was not finalized and it’s possible more senators, including other presidential contenders, will attend. The group is using the rally to unveil a plan to pressure 2020 Democrats to make the Green New Deal's goals a focus of their campaign, headlined by a planned demonstration at the second Democratic debate this July in Detroit.

Environmental groups, which range from grassroots activists to established groups like the League of Conservation Voters to organizations backed by megadonors Michael Bloomberg and Tom Steyer, are pushing candidates to release plans and commit to pursuing them early in their presidency.