The CEO of the nation's largest health insurer on Tuesday sharply criticized "Medicare for all" proposals being debated by Democratic lawmakers and presidential hopefuls, weighing in on a major political fight ahead of the 2020 election.

Medicare for all would amount to a “wholesale disruption of American health care [that] would surely jeopardize the relationship people have with their doctors, destabilize the nation’s health system, and limit the ability of clinicians to practice medicine at their best,” UnitedHealth Group CEO David Wichmann said on a conference call.

Wichmann said the costs of Medicare for all would “surely have a severe impact on the economy and jobs — all without fundamentally increasing access to care.” ADVERTISEMENT

Health insurance companies oppose Medicare for all, as the most sweeping version of the idea would effectively eliminate the role of private insurance and replace it with Medicare, the government-run health insurance program.

Insurers have been actively working to prevent any version of such legislation from being discussed. They are pushing for lawmakers to work on more moderate proposals, like strengthening ObamaCare and repairing what Democrats refer to as the Trump administration’s “sabotage” of the health law.

But Wichmann’s comments represent an escalation, as companies have been hesitant to wade directly into the scrum. Most of the work has been done by advocacy groups or lobbyists.

UnitedHealth was publicly called out by Sen. Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE (I-Vt.), who is running for president, after CEO Steve Nelson was heard on leaked audio telling employees that the company was actively working to undercut support for Medicare for all.

“Our message to Steve Nelson and UnitedHealthcare is simple: When we are in the White House your greed is going to end,” Sanders tweeted last week.

Medicare for all has become a litmus test among 2020 Democratic presidential contenders, as well as progressives in Congress.

Most of the Democratic presidential candidates, mindful of the progressive base in a primary, have endorsed single-payer health care proposals, including Democratic Sens. Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (Calif.), Cory Booker Cory Anthony BookerBipartisan praise pours in after Ginsburg's death DHS opens probe into allegations at Georgia ICE facility Democratic lawmakers call for an investigation into allegations of medical neglect at Georgia ICE facility MORE (N.J.) and Elizabeth Warren Elizabeth WarrenDimon: Wealth tax 'almost impossible to do' CNN's Don Lemon: 'Blow up the entire system' remark taken out of context Democrats shoot down talk of expanding Supreme Court MORE (Mass.), though some have also touted more incremental solutions.

Sanders, considered to be a top 2020 candidate, has made his Medicare for all plan a center point of his second presidential campaign, with no room for compromise or other proposals that would take incremental steps toward universal coverage.

But in Congress, legislation is a long shot. Democrats would need to win control of the White House as well as sizable majorities in the House and Senate to be in a position to advance any such proposal.

Democrats are also far from united on the issue. Some moderate lawmakers and Speaker Nancy Pelosi Nancy PelosiHoyer: House should vote on COVID-19 aid — with or without a bipartisan deal Ruth Bader Ginsburg lies in repose at Supreme Court McCarthy threatens motion to oust Pelosi if she moves forward with impeachment MORE (D-Calif.) have expressed concerns about the cost, and Pelosi has shown little indication that a House bill would get a floor vote this year.

Sanders discussed his Medicare for all plans during a Fox News town hall on Monday night, receiving cheers when host Brett Baier asked the audience if they would be willing to give up their employer-sponsored insurance and switch to a government-run plan.

Wichmann said UnitedHealth wants to achieve universal coverage, but not at the expense of a government takeover of health care.

“The path forward is to achieve universal coverage, and it can be substantially reached through existing public and private platforms," Wichmann said.