BALTIMORE — House Minority Leader Nancy Pelosi Wednesday threw cold water on a proposal by Democratic presidential candidate Bernie Sanders to implement a single-payer health care system and the increased taxes needed to create it.

"He's talking about a single-payer system and that's not going to happen," the California Democrat told reporters at the start of the House Democratic retreat in Baltimore.

"There is no use having a conversation about something that is never going to happen," she added later.

Pelosi was a key architect in the development and passage of the Affordable Care Act, which cast aside the idea of a single-payer system in favor of subsidies, the expansion of Medicaid and the creation of a health insurance marketplace.

Pelosi was once an advocate of a single-payer system, but it lacked support in Congress, even when Democrats controlled both chambers.

Sanders has revived the idea partly because of the many criticisms of Obamacare concerning high costs, huge deductibles and lack of choice.

Sanders is proposing everyone receive Medicare, which now serves only those in their 60s and older.

"It's a very popular idea in our country," Pelosi acknowledged. "But we have made a decision of where we are going with health care."

Pelosi said Obamacare includes many characteristics of a single-payer system, including the elimination of lifetime limits and ensuring the eligibility of people with pre-existing conditions to sign up for health insurance.

"Right now we are proud of what we have and we want to build upon that," Pelosi said.

She also rejected the proposal by Sanders to pay for universal health care with a tax increase.

"We are not running on any platform of raising taxes," Pelosi said, adding that Democrats will propose "a fairer tax system" this year.

Democrats have typically supported closing tax loopholes that hit the wealthy and expand savings for lower-income earners.