Congress needs to reach a deal to fund payments to Obamacare insurers by the end of September if lawmakers want to avoid even heftier price increases for customers, experts say.

The deadline illustrates the major task Congress faces as it tries to reach a bipartisan deal to fund cost sharing reduction payments, known as CSRs, to reimburse insurers for reducing out-of-pocket costs for low-income Obamacare enrollees next year. If negotiations spill into October, it may be too late to reduce premiums for enrollees next year, some experts say. The White House has not said if it intends to make the payments.