"This is the fight of our lives".
Trump's campaign described Warren as a "fraud".
"Millions and millions and millions of families are struggling to survive in a system that has been rigged", the senator said. "It is not right".
According to multiple sources familiar with the plans, Kennedy - a former student of Warren's - will introduce Warren and in part discuss why he believes Warren's record on economic issues will set her apart from the rest of the field from Lawrence, Massachusetts.
Warren did not refer to her Native American claims, but she repeatedly mentioned race and the added difficulties confronting minorities.
Warren is counting on performing well in next year's primary in New Hampshire, where Democrats have tended to favor candidates from nearby states in open primary years.
Weaving specific policy prescriptions into her remarks, from Medicare for All to the elimination of Washington "lobbying as we know it", Warren avoided taking direct jabs at US President Donald Trump.
Despite their similarities, Ms Warren and Mr Sanders have taken somewhat divergent paths in recent months as they prepare for the primary. Warren ultimately apologized to the Cherokee Nation.
"America's middle class is under attack", Warren said in the announcement video in December.
"It won't be enough to just undo the awful acts of this administration", Warren said.
Tracey Peters, an Andover resident who attended the Lawrence event, said she'd like to better understand why the senator has drawn criticism for speaking her mind.
Warren, a former law professor at Harvard University specializing in bankruptcy and commercial law, was a key architect of Barack Obama-era regulations to protect consumers from predatory lenders.
Warren seemed to be setting a progressive tone for her campaign.
She also spotlighted her push for increased government involvement in child care, college, infrastructure, clean energy, and the Green New Deal.
And Warren's launch comes at a challenging moment for the 69-year-old senator. "Like the women of Lawrence, we are here to say enough is enough!"
But Warren showed nothing but pride in Lawrence's pro-worker history. "I am in that fight all the way", she said. "I am in this fight all the way".
President Trump wasted little time Saturday before needling newly declared presidential candidate Elizabeth Warren over her controversial efforts to align herself with Native Americans. "Warren took and released a DNA test last fall confirming she has some ancestry dating six to 10 generations ago, but that did little to defuse Trump".
Warren and the other women running so far, among whom are Senators Kamala Harris and Kirsten Gillibrand, are hoping to build on the success of women candidates who played a significant role in Democrats regaining control of the U.S. House of Representatives in November's congressional elections.
She will also need to win over female voters, which might explain the highly unusual - and somewhat risky - decision to include a story about potty-training her baby daughter.
The enmity between the two politicians is no secret, but Warren focused on emphasizing the policies she wanted to enact rather than criticizing those now in use.