A day ahead of his expected official announcement, the senator from the northeastern US state of Vermont spoke to US media outlets confirming his intentions to run against Hillary Clinton.

"People should not underestimate me," Sanders told the Associated Press news agency in an exclusive interview. "I've run outside of the two-party system, defeating Democrats and Republicans, taking on big-money candidates and, you know, I think the message that has resonated [in my home state] is a message that can resonate all over this country."

In an interview with USA Today, he underlined his campaign strategy of appealing to voters' wish for "a fundamental change so that government works for ordinary Americans and not just billionaires."

The 73-year-old Independent has earned a reputation as one of the most liberal politicians on Capitol Hill during his 25-year tenure in Congress. He served in the US House of Representatives from 1990 to 2006, and was then elected to the US Senate where he continues to hold a seat.

Thus far, Clinton, has been the only Democrat to put her name forward for what is expected to be the most expensive presidential campaign in US history.

Before each party can nominate a candidate, contenders must run against fellow party members in state-by-state elections, known as the primaries, slated to begin in February 2016.

The man of the 99%

In the lead-up to his official announcement, which is expected on Thursday, Sanders made clear his intentions of reforming the tax system to revive the middle class by slapping "the top 1%" with heavier taxes.

He also took aim at the billionaire Koch brothers, who have announced a 2016 campaign finance budget of nearly $900 million (810 million euros), which is expected to boost the Republican Party's presidential and congressional candidates.

Earlier this month, Sanders also took aim at Democratic presidential contender Hillary Clinton's ties to American wealth and power in bid to undermine her credibility.

"I do have doubts about whether Hillary Clinton or whether any Republican candidate out there is prepared to take on the big money interests who control so much of our economy," he told US broadcaster Fox News earlier this month.

Clinton, he said, would have to convince the American people that, despite her past record, "she is going to break up the major banks on Wall Street."

In addition to his support for higher taxes and tighter regulation, Sanders has also previously opposed international trade agreements, including the Trans-Pacific Partnership, or T.P.P., which he attributes to the demise of American manufacturing.

Small fish in a big pond

A champion of the American worker and a politician from a state with one of the lowest populations in the US, Sanders would face a huge fundraising challenge in an era where private interests can keep their preferred candidates afloat with unlimited funding under the protection of so-called Super PACs.

Hillary Clinton has already set a $100 million budget goal for the Democratic primary race, which is only the first leg of the race to become the president of the United States.

kms/bw (AP, Reuters)