Democratic Sen. Elizabeth Warren on Thursday declared it is "time for us go on the offense" on healthcare as she presented incremental changes to Obamacare.

"We will defend Medicaid and the Affordable Care Act with everything we have. We will defend it, all the way," said the Massachusetts Democrat, using the formal name for Obamacare. "We need to do more than play defense ... I believe it is time for us to go on offense."

Warren, who is considered a potential candidate to challenge President Trump in the 2020 election, was speaking at a conference for Families USA, a pro-Obamacare group. She praised the strides that Obamacare had made but noted that 28 million people are still uninsured.

She offered more government restrictions on what private health insurance companies can do. They would include prohibiting insurers from providing narrow networks of doctors who patients can see, dropping coverage for a prescription in the middle of the year, or leaving the Obamacare exchanges.

Insurers, she said, should be held to the same out-of-pocket cost standards as those set by Medicare and Medicaid, which are funded by the government.

She proposed as well that insurers that contract with Medicare and Medicaid, which she said results in hundreds of billions of dollars in profits, should be required to also offer coverage on the Obamacare exchanges. The exchanges allow people who don't get coverage through work or through a government program to buy a tax-subsidized plan.

If insurers say the changes are impossible, Congress needed to "call their bluff," she said.

"If the insurance company walks, we should replace their policies with public alternatives," she concluded.

Warren skewered private health insurance companies throughout her speech, saying their practices put profits before their customers and that "taxpayers have helped make insurance companies wildly profitable."

"Private insurance companies are failing the American people ... there is no reason on earth for us to continue to allow the healthcare of the American people to be held hostage by an industry that both attacks any new healthcare proposals and at the same time refuses to do anything to fix it," Warren said.

She also voiced support for other proposals from Democratic colleagues in the Senate, including allowing people to purchase a public option from the Obamacare exchanges or allowing people to buy into Medicaid.

The single-payer plan proposed by Sen. Bernie Sanders, I-Vt., has support from 16 Democratic senators, including Warren.

Warren said the Sanders plan "lays out a way to give every single person in this country a guarantee of high-quality coverage," adding, "this is a goal worth fighting for and I am in this fight all the way."

The proposal, called the Medicare for All Act, would remove people from private coverage and put them in a government-funded system. The bill does not include information about funding mechanisms.

Warren worked to defend Obamacare against repeal in 2017. Larger bills ultimately failed without adequate Republican support. The GOP Congress did pass a tax bill that contained a repeal of the penalties that required people buy health insurance or pay a fine.