With a deadline looming, California’s health exchange and a major insurer pressed Republican leaders in Washington to clear up confusion over their commitment to key provisions of the Affordable Care Act.

Health insurers participating in the Covered California exchange for individuals and families must submit initial rates for 2018 on Monday. Peter Lee, the exchange’s executive director, warned in a conference call Thursday that rates could jump by more than 40 percent if the Trump administration and Republican-led Congress walk away from crucial elements of the health law.

In the meantime, House Republicans are looking to revive their Obamacare replacement bill and rally more support among moderate lawmakers in hopes of holding a vote soon.

In addition to Covered California, the chief executive of Molina Healthcare, a Long Beach-based insurer, implored Congress and the Trump administration on Thursday to act quickly to stabilize the exchange markets.

At issue are the continued federal funding of subsidies that reduce low-income consumers’ deductibles and copays and the enforcement of the individual mandate to purchase health coverage or pay a penalty.

Premiums in Covered California plans could increase by 42 percent, on average, if those subsidies aren’t funded and the mandate isn’t enforced, according to an analysis released Thursday by the exchange. Covered California has about 1.3 million customers.

Lee said it is imperative for leaders in Washington to clear up the uncertainty to avoid damaging insurance markets nationwide and hurting consumers. He said statements this week by the Trump administration that it would continue funding the cost-sharing subsidies haven’t specifically addressed whether that applies to all of 2017 or 2018.

“Health plans need to know now what are the rules of the road,” Lee said. “Insurers are considering their participation in the face of unprecedented uncertainty.”

Much of the debate this week in Washington has centered on House Republicans amending their Obamacare replacement bill, the American Health Care Act. But Lee said addressing the current market rules should be a priority ahead of crafting broader legislation.

Lee declined to comment on the latest legislative proposal from House Republicans, but he noted it still faces a long road ahead in Congress before it would win approval. “Health plans need to submit bids for today’s reality. Policymakers need to address that reality,” Lee said.

In a letter to House Speaker Paul Ryan and other congressional leaders, Molina Healthcare CEO J. Mario Molina said the cost-sharing reduction subsidies are essential for making coverage affordable for many consumers. Those subsidies cover out-of-pocket costs for exchange customers with incomes below 250 percent of the federal poverty level. They are separate from the tax credits that subsidize premium costs.

Without that federal funding, Molina wrote, “we will have no choice but to send a notice of default informing the government that we are dropping our contracts for their failure to pay premiums and seek to withdraw from the marketplace immediately.”

Molina said his company currently serves more than 1 million people through insurance exchanges in California and several other states. Molina had nearly 69,000 enrollees in Covered California as of December, state data show.

Anthem, California’s largest for-profit health insurer and a key player on exchanges nationally, issued a similar warning this week. During an earnings conference call on Wednesday, Anthem CEO Joseph Swedish said the insurer may exit some state exchanges or resubmit for higher rates if the fate of the cost-sharing subsidies isn’t resolved by early June.

Anthem has more than 310,000 customers in the California exchange, or nearly 25 percent of the market. Rival Blue Shield of California is the leader in state enrollment with 389,480, or 31 percent market share.

Republican leaders in Congress say they will address these concerns and move quickly to aid consumers by replacing the ACA with a plan that will reduce premiums and expand options for coverage.

The health law “is collapsing,” Ryan said at a news conference Thursday. “The American health care system in the individual market is in peril right now. We have a moral obligation to prevent people from getting hurt, to stop the damage from being continued.”

Many conservative Republicans oppose the Trump administration’s decision to continue to pay the cost-sharing subsidies, calling the subsidies unconstitutional because they lack congressional approval. House Republicans successfully sued to block the payments, but a judge put the ruling on hold while the Obama administration appealed the case. It’s not yet clear how President Donald Trump will handle that appeal.

Amid this political uncertainty, California Insurance Commissioner Dave Jones told insurers this week they could submit two sets of rate filings on Monday for their exchange business. One filing would reflect continued funding of cost-sharing subsidies and enforcement of the individual mandate. A separate filing could assume the opposite.

“In light of all the actions taken by the Trump administration and House leadership to undermine the ACA, I expect that health insurers will consider filing significant rate increases for 2018,” Jones wrote in a bulletin to insurers this week.

For 2017, rates in Covered California rose by 13.2 percent, on average, statewide. The state exchange is one of the few that actively negotiates rates with insurers. Premiums for the next year usually are announced in July.