WASHINGTON – Minnesota's efforts to drive down premiums for coverage sold on the state health insurance exchange could come undone by the end of the month unless the federal government acts.

After seven years of partisan wrangling over Obamacare, U.S. senators worked Tuesday to hammer out a bipartisan fix they hope could stabilize state insurance exchanges before millions of Americans are hit with rate hikes. The CEO of MNsure, Minnesota's exchange, told a Senate panel Tuesday that the state may have mere days left to avoid the kind of hikes that state lawmakers took expensive steps to avoid earlier this year.

Even as federal lawmakers consider short-term repairs to the Affordable Care Act, a growing number of Democrats including Sen. Al Franken are looking more long-term. The Minnesota Democrat announced Tuesday that he has signed on as a cosponsor of Vermont Sen. Bernie Sanders' "Medicare for All" single-payer health care plan, calling health care "a right for all Americans."

In the short term, Franken — a member of the Senate Health, Education, Labor and Pensions Committee that's trying to address the most urgent problems — said the Senate needs to "pursue bipartisan policies that improve our current health care system for all Americans."

A fix can't come fast enough for Minnesota officials.

"Premiums remain too high and provider networks too narrow for many Minnesota families," MNsure CEO Allison O'Toole told the Senate panel. "Action at the federal level is needed to add certainty, stability and strength to individual markets across the country."

The committee's leaders, Republican Sen. Lamar Alexander of Tennessee and Democratic Sen. Patty Murray of Washington, hope to come up with a stabilization plan before insurance companies lock in their 2018 rate plans at the end of September.

"What can Congress and the president do, between now and the end of the month, to help limit premium increases in 2018 and lower premiums after that?" Alexander said as the committee began the third of four September hearings on a stabilization plan.

Republicans want to give states more flexibility to waive Affordable Care Act requirements and tailor their own plans, prices and coverage levels, without battling through thickets of federal red tape. Democrats want to preserve the so-called guardrails in the program that prevent insurers from offering flimsy plans that wouldn't protect a customer from catastrophic medical bills.

The Affordable Care Act already lets states seek waivers to try new ways to keep costs down and citizens covered. Minnesota is seeking one now for its plan to spend $271 million a year for the next two years on a reinsurance program that would help health plans cover expenses for patients with high-cost conditions.

Reinsurance could lower Minnesotans' premiums by 20 percent from where they otherwise might be, but only if the waiver is approved, O'Toole said.

"If our waiver is not granted in the next few days, Minnesotans will be paying substantially higher premiums next year," O'Toole told the senators in the crowded hearing room. "That's not speculation, that's fact."

O'Toole offered up a quick list of fixes that senators could implement to shore up state programs, including a federal reinsurance system. State-level programs like Minnesota's would not be sustainable in the long run, she said. She also hopes Congress will make long-term provisions for the cost-sharing reduction payments to health plans that participate in the ACA — payments thrown into doubt after President Donald Trump derided the subsidies as "insurance company bailouts."

Franken joined a growing number of Democratic colleagues in the Senate in aligning with Sanders' single-payer proposal. In coming out for the plan, Franken invoked the late Minnesota Sen. Paul Wellstone, a longtime advocate of a single-payer health care model.

"Like Paul Wellstone, I've always believed that health care is a right for all Americans — not a privilege — and that every person in our country deserves access to the care they need," Franken said in a statement. "Establishing a single-payer system would be one way to achieve universal coverage, and Senator Sanders' 'Medicare for All' bill lays down an important marker to help us reach that goal."

Star Tribune reporter Christopher Snowbeck contributed to this story.

Jennifer Brooks • 202-662-7452