Image copyright Karen Ducey/Getty Images Image caption Governor Inslee after speaking at a rally during the March for Science on April 22, 2017 in Seattle, Washington

Washington State's Democratic Governor Jay Inslee has announced his 2020 bid for the US presidential nomination, joining a lengthy list of contenders.

Mr Inslee, 68, will make climate change his number one issue, calling it "the most urgent challenge of our time" in his first campaign video.

He is the first governor to throw his hat into the ring, joining 12 other Democrats, including six senators.

The two-term governor has been a fierce critic of President Donald Trump.

"I'm running for president because I am the only candidate who will make defeating climate change our nation's number one priority," Mr Inslee says in the video, released on Friday.

Mr Inslee's mid-term elections campaign ran on the platform of creating new energy jobs - his 2020 campaign video echoed the same, tying "defeating climate change" with transforming the economy.

At a news conference on Friday, Mr Inslee said his national mission would focus on powering the economy with 100% clean energy, creating jobs, and focusing on "justice and inclusion...so no group is left to bear the cost of transition".

"We are going to build electric cars in Michigan, we are going to build and install wind turbines in Iowa, we are going to install solar right here in Washington State," Mr Inslee said.

Image copyright CBS Image caption Mr Inslee will start campaigning next week

In addition to his environmental efforts, Mr Inslee announced his other big proposals: raising the minimum wage, legalising marijuana, protecting net neutrality, investing in infrastructure and pushing for gun control.

"We've banned bump stocks and we're not done - let's ban assault weapons and take weapons of war off our streets," he said.

Mr Inslee will begin his campaigning efforts in Iowa on Tuesday and Nevada later next week, US media report.

Elizabeth Warren, Kirsten Gillibrand, Amy Klobuchar, Kamala Harris and Bernie Sanders are among other declared contenders for the Democratic primary in 2020, the first time more than one woman has competed.

Unmatched progressive credentials

Jay Inslee is someone who in the past would be a naturally formidable presidential candidate. He's a veteran politician with the kind of executive experience that comes from being a governor of a mid-sized state.

At a small session at the liberal Netroots Nation conference last August, the 68-year-old Inslee displayed a low-key confidence and command of the issues, with the kind of self-deprecating wit that can be effective disarming critics. He won't light up a stage like Senator Cory Booker or potential candidate Beto O'Rourke, but he's a comfortable public speaker.

This isn't your father's Democratic Party, of course, and with a diverse range of candidates already in the race, Mr Inslee will be pressed to find breathing room for his campaign.

His answer is to fashion himself as the environmental candidate.

With the Green New Deal getting traction among progressives, Mr Inslee is touting his work addressing climate change in Washington state. He's launching his presidential bid at a solar panel factory whose success he attributes to his policies as governor.

If Mr Inslee gets the attention of Democratic voters with his environmental pitch, he can then pivot to talking about his efforts to fight the Trump administration's immigration policies, expand healthcare in his state, raise the minimum wage, enact paid family medical leave, end capital punishment and pardon Washington residents previously convicted of now-legalised marijuana drug offences.

It's a record of progressive accomplishment that the half-dozen senators already in the race, having toiled in the minority since 2014, can't match.

Who is Jay Inslee?

Jay Inslee is a fifth-generation Washingtonian, born and raised in Seattle.

He is a former prosecutor and former congressman who represented the state of Washington in the House of Representatives for several terms in the 1990s.

His father was a high school science teacher who helped spark his love of nature.

Mr Inslee won the governorship in 2012, defeating a Republican and replacing Democratic incumbent Christine Gregoire. He took the seat after winning only eight counties out of the state's 39, losing the rural vote to his conservative opponent, according to the New York Times.

He was the chairman of the Democratic Governors Association in 2018, helping with campaigning efforts across the country.

In December, he compared his presidential hopes with those of Jimmy Carter and Bill Clinton, saying both former presidents were "unknown governors of small states" before winning the presidency, the Seattle Times reported.