 -- It was a big day on Capitol Hill for Sen. Bernie Sanders and the debate over health care policy in the United States. Surrounded by a dozen of his Democratic colleagues, nurses, doctors and patient advocates, the Vermont introduced the latest version of his health care bill Wednesday, a proposal he refers to as "Medicare for all."

"Today, all of us stand before you and proudly proclaim our belief that health care in America must be a right, not a privilege," Sanders said.

Sanders' bill, based on an idea central to his 2016 presidential bid, would open up the current Medicare insurance program to all American citizens and residents. The federal government would pay the cost of insurance, premiums, deductibles and most co-pays, effectively eliminating the majority of out-of-pocket medical costs for Americans. Like with the current Medicare system, patients would still primarily receive medical services at private institutions. Matt Fielder, a health care policy expert at the Brookings Institute describes the concept this way during an interview with ABC News, "Single payer is about who pays the bills not who delivers the care."

Sanders' bill does not attempt to answer the question of financing, how the government would pay for the significant expenses his proposal would require. While the plan has not received a score from the Congressional Budget Office, experts have estimated the proposal could cost the government approximately $3 trillion a year.

"While, depending on your income, your taxes may go up to pay for this publicly funded program, that expense will be more than offset by the money you are saving by elimination of private insurance costs," he continued during his fiery speech on Capitol Hill on Wednesday.

He said U.S. health care is in a "crisis" and that special interest groups have contributed to rising costs.

"The crisis is a political crisis that speaks to the incredible power of the insurance companies, the drug companies and all those who make a billions of dollars off of the current system," Sanders said. "Over the years these entities have done everything they can do to prevent us from having lower drug prices and universal health care."

Here's a closer look at some of the bill's proposals:

The bill includes a transition period. In the first year, children up to age 18 and adults over 55 would be eligible for Medicare. (Currently, most Americans are not eligible until they are 65.) Over the next three years the pool would be increased, until eventually citizens and permanent residents of all ages were eligible for the government insurance program, which would cover essential health benefits such as emergency services, primary and preventive services, ambulances, maternity care, substance abuse care and other services.

The bill also calls for the services and care covered by traditional Medicare to be expanded to include dental, vision and hearing aids.

The bill allows the federal government and expanded Medicare system to negotiate drug prices.

Medicaid, veterans insurance programs and hospitals and other government run insurance programs would remain.

Private insurance companies could still offer private coverage plans to supplement the Medicare coverage.

During the transition period, the federal government would offer a so-called public insurance option that would compete against private insurance plans in individual insurance marketplaces.

Elizabeth Warren described the proposal as a plan to build on the Affordable Care Act, though the bill would in fact take a very different approach. Instead of the government subsidizing private insurance, Sanders' bill would create a government-run insurance program.

"Barack Obama, who helped build the game changer that gave millions of Americans, who didn't have health care coverage, new health care coverage. We are here today to take another step. We will not back down in our protection of the Affordable Care Act. We will defend it at every turn. But we will go further. And we will say that in this country everyone, everyone gets a right to basic health care," she said.

Dr. Danielle Martin, a Canadian physician, discussed the benefits of universal coverage at the event on Capitol Hill. "My generation of Canadians does not remember what it was like to worry about paying a doctor or hospital bill."

Sen. Corey Booker, D-N.J., a co-sponsor on Sanders' bill, lamented that other developed nations had found ways to provide universal coverage and limit costs, while still experiencing health care outcomes at times better than those in the United States.

"This is a defining moment of the character of our country. How can we get the greatest nation on the planet earth have the most expensive health care system," Booker said, adding. "It is embarrassing to me ... to have a Canadian stand here in the capital of the United States of America and talk about a system that takes care of their children better than we take care of our children."

Fiedler said that countries with socialized systems of health care have been able to cut costs.

"It is certainly the case that other countries spend considerably less on health care," Fiedler told ABC News in a phone interview. "A big component is they pay the medical providers, doctors and hospitals and drug manufacturers, less than we do in the United States. It is quite plausible that a single-payer system, because of the bargaining power of the single payer would have, at least in principle, could wring out some of those savings from the U.S. system."

Still, Fiedler added that many questions remain about how exactly a program like Sanders' would work in the United States.

"The federal government would now be paying for health care for more than 150 million people who now get their health insurance through the private market and that would be very expensive. I think question to financing to pay for that care is a hard one," he went on. "I think that transition would be a messy one."