Socialist lawmaker Alexandria Ocasio-Cortez has turned her firepower on Joe Biden and given her blessing to a little-known 2020 candidate's environmental plan - days before the former vice president is set to unveil his own proposal.

Ocasio-Cortez endorsed Washington Gov. Jay Inslee's climate plan as 'the most serious + comprehensive one to address our crisis in the 2020 field.'

She praised its meeting of 'key marks,' including 'being big enough, fast enough, economically stimulating for working people, acknowledges injustice + w/ an eye to make communities whole' in a tweet on Saturday.

Using her bully pulpit as the social media star of the Democratic party is a power play by Ocasio-Cortez.

Rep. Alexandria Ocasio-Cortez turned her fire power on Joe Biden when she gave her blessing to a little known 2020 candidate's environmental plan

Her move came days before Joe Biden is to release his own climate proposal

Her endorsement comes as Biden, the frontrunner for the Democratic presidential nomination, has promised to reveal his own environmental plan by the end of the month.

'The first and most important plan in my climate proposal is beat Trump,' Biden said on Saturday at a rally in Philadelphia.

It's not the first time the young, freshman lawmaker from New York has clashed with the 76-year-old former vice president on climate issues.

And it's another sign from Ocasio-Cortez, a rising star among the left in the Democratic Party, that she plans to make her weight felt in the Democrats' battle for the right to take on President Donald Trump next year.

Her endorsement would be seen as a blessing from the left - an important voting bloc in the primary contest; harness her star power and fundraising prowess; and help a candidate stand out from the crowded pack of 24 contenders.

She has teased as to who might get her blessing.

In addition to her support for Inslee's plan, earlier this month she appeared alongside Bernie Sanders in a video co-introducing legislation that would cap credit card interest rates at 15 per cent, saying she's happy she's able to introduce legislation in both chambers of Congress with a good 'working partner.'

And, last week, Ocasio-Cortez slammed politicians who took a 'middle of the road' approach to climate change, an apparent critique of Biden.

While she never mentioned him by name, Ocasio-Cortez retweeted a linked to a Reuters article reporting Biden 'is crafting a climate change policy he hopes will appeal to both environmentalists and the blue-collar voters who elected [Trump].'

She slammed the idea with her own added commentary: 'This is a dealbreaker. There is no 'middle ground' w/ climate denial & delay. Blaming 'blue collar' Americans as the main opponents to bold climate policy is gas lobbyist 101. We're not going to solve the climate crisis w/ this lack of leadership. Our kids' lives are at stake.'

In contrast, she praised a plan from Inslee whose climate leadership she has called 'phenomenal.'

Ocasio-Cortez also appeared along side Bernie Sanders in a video touting their legislation to crack down on credit card fraud

Inslee's plan, the '100 Percent Clean Energy for America Plan,' would require all coal-fired power plants to be closed in a decade and put the U.S. on track to reach net-zero emissions by 2045.

He's not the only candidate out with a progressive plan for the planet along the lines of the Green New Deal that Ocasio-Cortez and liberals are pushing.

Beto O'Rourke called for $5 trillion to be spent over the next decade to ensure the U.S. neutralizing carbon emissions by mid-century.

And Sen. Michael Bennet unveiled a plan Monday that calls for net zero emissions by 2050 and creates a 'Climate Bank' to spur $10 trillion in investment.

Younger, more progressive Democratic voters have named climate change one of their top issues.

Biden defended himself against her charges at a campaign stop in New Hampshire last week.

'You never heard me say middle of the road. I've never been middle of the road on the environment,' Biden told reporters at The Works Cafe in Concord, New Hampshire. 'Tell her to check the statement that I made and look at my record. She'll find that nobody has been more consistent than taking on the environment and the green revolution than I have.'

'I don't think she was talking about me,' Biden added.

He wore a 'PROTECT PEOPLE, NOT POLLUTERS' sticker on his lapel during the campaign stop, which came on the second day of his two-day swing through New Hampshire.

He added that 'you'll hear very shortly the totality of what I plan on doing.'

Biden told New Hampshire voters on Monday that he'll deliver his policy plans on the environment by the end of the month.

'I'm laying out a major speech in detail by the end of the month on my specific pieces on the environment. We need an environmental revolution,' he said at a pizza parlor in Hampton, New Hampshire.

But, he noted, 'we do need to finish this green revolution in a way that's rational.'

Ocasio-Cortez also was fired up about the issue last Monday night at an event in Washington, where she was trying to rally support for her legislative agenda.

'I will be damned if the same politicians who refused to act then are going to try to come back today and say we need to find a middle-of-the-road approach to save our lives,' she said.

'That is too much for me,' she added.