The Massachusetts senator on Tuesday unveiled a plan she said would make the process of declaring bankruptcy easier and cheaper for many Americans with debts they can't pay. It also would largely undo a 2005 law that was backed by Biden and financial industry interests with a lot of political clout in his home state of Delaware. Warren, then a bankruptcy expert and professor at Harvard Law School, clashed with then-Sen. Biden while the law was being debated in Congress — a dust-up she referenced in announcing her new plan.

"By making it harder for people to discharge their debts and keep current on their house payments, the 2005 bill made the 2008 financial crisis significantly worse: experts found that the bill 'caused about 800,000 additional mortgage defaults and 250,000 additional foreclosures,'" Warren wrote in an online post. "And despite the claims from the industry and their allies in Congress that the 2005 bill would reduce credit card costs across the board for consumers, the cost of credit card debt went up too."

"I lost that fight in 2005, and working families paid the price," she added.

It's a sign that Warren is seeking to shift focus to domestic policies that have made her the candidate who "has a plan" for top issues at a time when the 2020 campaign could be consumed by rising U.S. tensions with Iran. That's potentially a strength for Biden, given his experience with foreign policy in the Senate and the Obama administration.

Biden spoke Tuesday in New York about President Donald Trump's decision to approve an airstrike that killed Iranian Gen. Qassem Soleimani. His remarks follow several days of campaigning in which he seemed uncertain of how much to highlight his foreign policy resume.

Warren has also talked about Iran, calling Soleimani's killing an assassination, and she issued a fresh call for de-escalation in the region at the start of her own New York rally with Julián Castro on Tuesday night. Speaking shortly after Iran launched missiles at bases housing U.S. troops in Iraq, Warren told the crowd of thousands that "my heart and my prayers are with our military and their families in Iraq and all around the world."

She added that "this is a reminder why we need to de-escalate tension in the Middle East. The American people do not want a war with Iran."

Tuesday's bankruptcy plan is especially close to Warren's heart. As a law professor at the University of Texas, she studied bankruptcy cases  nationwide and concluded that, rather than overspending, many people declaring bankruptcy were doing so because the economy "forced them to take on more debt and more risk to cling to their place in America's middle class. And that meant one bad break could send them tumbling over the edge."

Her extensive study of and writings on bankruptcy made her an expert on the subject when she moved to the faculty of Harvard Law School — and helped prompt a fight with Biden, seven years before Warren was elected to the Senate.

During a Senate hearing in 2005, Warren and Biden went back-and-forth, with Biden mentioning credit card companies and saying the problem was not with a bankruptcy proposal that eventually would became law but with borrowing rules. Warren responded, "You can't take away the last shred of protection for these families," which prompted Biden to concede, "You're very good, professor."

Now that Warren is saying she wants to roll back many of those provisions, some of her supporters see a showdown coming.

"When thinking about electability, it would be complete malpractice to nominate someone who conspired in backrooms for years with credit card lobbyists and voted for every corporate bankruptcy bill, Wall Street deregulation, and trade deal that voters hate," Adam Green, co-founder of the Progressive Change Campaign Committee, said in a statement. "Biden would ironically cede the outsider mantle to a corrupt incumbent president."

Biden's campaign on Tuesday pointed to a statement that spokesperson Andrew Bates previously released on the 2005 law, saying the then-senator "fought for and won important concessions for middle class families in it."

Warren has feuded for weeks with another candidate bunched with her and Biden for Democratic primary front-runner status: former South Bend, Indiana, Mayor Pete Buttigieg.

Sharpening her rhetoric against Biden would put Warren more in line with a fellow White House hopeful competing for the Democratic Party's left flank, Vermont Sen. Bernie Sanders. He has for months criticized the former vice president, including saying Monday on CNN that Biden once wanted to cut Social Security and Medicare while in the Senate.

Warren says her plan will also "end the absurd rules that make it nearly impossible to discharge student loan debt in bankruptcy" and allow for many of those doing so to keep their homes and cars "so they can start from a firm foundation when they start to pick up the pieces and rebuild their financial lives." She also said she'd work to address "shameful" racial and gender disparities in the current system.