A bipartisan group of governors are criticizing the Republican health care bill currently being crafted in Congress, arguing the legislation fails to protect the vulnerable and shifts the financial burden of coverage to the states.

In a pointed letter to Senate Majority Leader Mitch McConnell and Minority Leader Chuck Schumer, the Republican and Democratic governors called on senators to engage with them in the health care reform debate— arguing the current draft of the GOP's health care bill was insufficient to ensure adequate coverage and affordability.

"Improvements should be based on a set of guiding principles, included below, which include controlling costs and stabilizing the market, that will positively impact the coverage and care of millions of Americans, including many who are dealing with mental illness, chronic health problems, and drug addiction," the letter stated.

"Unfortunately, H.R. 1628, as passed by the House, does not meet these challenges," it added.

The group included Republicans John Kasich of Ohio, Brain Sandoval of Nevada, and Charles Baker of Massachusetts. Democrats Steve Bullock of Montana, John Bel Edwards of Louisiana, John Hickenlooper of Colorado, and Tom Wolf of Pennsylvania also signed on.

Earlier this week, President Donald Trump reportedly described the House bill as "mean," even as he celebrated its passage last month. Senate Republicans are working on their version of a bill, but have kept the negotiations largely shrouded from public view.

"We feel that true and lasting reforms are best approached by finding common ground in a bipartisan fashion," the governors wrote, laying out a set of principles that include improving affordability and stability to insurance.

They are also seeking flexibility for states to innovate, and less regulatory red tape.

The letter's signatories represent states that chose to expand the Medicaid program, in which the federal government pays at least 90 percent of the costs. However, that funding would be zero by 2020 under the House bill. "Medicaid provisions in this bill are particularly problematic," they wrote.

Governors from expansion states have been especially vocal about cutting funding to the states. The Congressional Budget Office (CB) estimates the House bill will knock 14 million people off the Medicaid who would otherwise have been covered.

In an interview with CNBC, Colorado Governor John Hickenlooper said, "Ultimately governors are the ones who are going to have to implement whatever they come up with, and I think it would be unfortunate if we are not part of that process of figuring out what are the best compromises cause."

Still, the governors believe there is common ground in driving down costs and stabilizing the marketplace, although Obamacare's passage in 2009 looms large over the negotiations.

"You cannot write major legislation with one party, it doesn't work," Kasich told MSNBC in a May interview. "Obama tried it, Obamacare is, you know, under fire every day. If Republicans do it, and they do it alone, it isn't going to last."

Here is the letter in its entirety: