The Senate legislation introduced last week to repeal and replace Obamacare falls short of addressing systematic problems in the U.S. healthcare industry, a Republican lawmaker who opposes the bill wrote in a New York Times op-ed published Monday.

Sen. Ron Johnson (R-Wis.), one of five GOP senators who has announced opposition to the repeal-and-replace measure, said the bill does not go far enough in undoing certain Obamacare provisions and follows too closely in the mold of past government solutions instead of taking problem-solving strategies from the private sector.

“Like many other senators, I had hoped that this was where things were headed during the last several weeks as the Republican bill was discussed,” Johnson wrote. “We’re disappointed that the discussion draft turns its back on this simple solution, and goes with something far too familiar: throwing money at the problem.”

With a 52-seat majority in the Senate, Republican leaders can afford to lose the support of just two members of their caucus and still pass the repeal-and-replace legislation that has been a top GOP priority for years. Republican leadership in the Senate has said the chamber will vote on the bill later this week.

Johnson said it was unacceptable that the GOP proposal leaves in place a provision banning insurers from denying coverage to those with preexisting conditions or charging them more, rules he said “drive up the cost of insurance for everyone.” Also unacceptable are increases for healthcare subsidies, he wrote.

In attacking Obamacare itself, the Wisconsin senator recalled the words of former President Bill Clinton, who described the healthcare legislation as “the craziest thing in the world” during a campaign stop on behalf of his wife, 2016 Democratic presidential candidate Hillary Clinton, a remark that quickly became a GOP talking point despite backtracking from the former president.

Obamacare, Johnson said, has “virtually eliminated the power of consumer-driven, free-market discipline from one-sixth of our economy.” He pointed to laser eye surgery, which grew cheaper and more prevalent when it was not covered by most insurance plans, as evidence that healthcare is not immune to market forces.

A better solution than the one currently on the table would further loosen regulations, Johnson said, “so that Americans can choose to purchase insurance that suits their needs and that they can afford.” The Wisconsin senator said protections for individuals with preexisting conditions should be modeled after on pre-Obamacare programs in states like his own, which previously relied on high-risk pools.

With regulations sufficiently loosened, Johnson wrote, “the market [can] begin to rein in the underlying cost of health care itself and reduce the cost of taxpayer subsidies.” He left open the option of working with Senate leadership to alter the bill enough for him to support it.

“Republican leaders have told us the plan unveiled last week is a draft, open to discussion and improvement,” Johnson wrote. “I look forward to working with Senate leadership and the president to improve the bill so it addresses the plight of the forgotten men and women by returning freedom and choice to health care.”