INDIANOLA, Iowa – Elizabeth Warren said she is planning to release information soon that outlines how she will pay for her "Medicare for All" plan.

The issue has followed the Massachusetts senator in at least two Democratic presidential debates as she has declined to say whether taxes will go up to pay for her proposal, which would abolish private health insurance in favor of Medicare for every American.

"Right now, the cost estimates on Medicare for All vary by trillions and trillions of dollars. And the different revenue streams for how to fund it – there are a lot of them," she said to a crowd of about 475 at Simpson College. "So this is something I’ve been working on for months and months and it’s got just a little more work until it's finished."

Warren is a cosponsor of U.S. Sen. Bernie Sanders' Medicare for All plan, introduced in the Senate more than two years ago. The senator from Vermont has said taxes will go up to pay for his plan, but all out-of-pocket expenses like co-pays, premiums and deductibles would be eliminated.

There's a new front-runner in town:Elizabeth Warren. Just ask her Democratic rivals

While Warren has been known to release robust policies and plans that detail ways to pay for them, she has yet to outline how she would pay for her public health care program.

The senator was asked pointedly by debate moderators last week whether taxes will go up to pay for her plan. Warren said her plan would reduce health care costs for middle class Americans but did not address how her plan would affect taxes.

"So, the way I see this, it is about what kinds of costs middle-class families are going to face," she said during the debate in Westerville, Ohio, last week. "So, let me be clear on this. Costs will go up for the wealthy. They will go up for big corporations. And for middle-class families, they will go down."

In Indianola on Sunday, Warren said she would not sign a Medicare for All bill "that does not reduce the cost of health care for middle class families."

Joe Biden digs at Elizabeth Warren:Polls don't show 'anybody else as a frontrunner'

"Because it is the cost of health care that is hurting families and the cost of health care is what they care about," she said. "And because they care about it, I care about it."

Her debate answer, however, paved the way for attacks from her Democratic rivals, particularly South Bend, Indiana, Mayor Pete Buttigieg who said Warren has failed to answer a yes or no question put forth by the moderators. He has released a plan that gives Medicare to anyone who wants it.

"At least Bernie's being honest here and saying how he's going to pay for this and that taxes are going to go up," added Sen. Amy Klobuchar of Minnesota, who supports a public option that would expand Medicaid and Medicare. "And I'm sorry, Elizabeth, but you have not said that, and I think we owe it to the American people to tell them where we're going to send the invoice."

Warren kicked off a three-day Iowa swing Sunday at a town hall in Indianola. She plans stops in Des Moines, Ames and Cedar Falls.

Follow Kim Norvell on Twitter: @KimNorvellDMR