Mr. Trump has repeatedly threatened to cut off the payments as a way to force Democrats to negotiate over the future of the Affordable Care Act.
The president can stop the payments because a federal judge ruled last year that the Obama administration had been illegally making the payments in the absence of a law explicitly providing money for the purpose. The Obama administration appealed the ruling, and the payments continue from month to month, with permission from the court. But Mr. Trump could drop the appeal and stop the payments at any time.
In its latest bulletin, the Trump administration said that many state insurance commissioners had allowed insurers to increase rates for 2018 to account for the “uncompensated liability” that they might face for the cost-sharing reductions.
The amount of the increases varies, but many insurers say that prices will be 15 to 20 percent higher next year because they do not know if they will receive the subsidies they are anticipating.
The future of the subsidies has been uncertain since Republican efforts to repeal major provisions of the Affordable Care Act collapsed last month in the Senate, where three Republicans joined all Democrats in voting down a proposal drafted by the majority leader, Senator Mitch McConnell of Kentucky. Mr. Trump chided Mr. McConnell for the failure and urged him to keep trying.
The impasse is already taking a toll.
“Planning and pricing for A.C.A.-compliant health plans has become increasingly difficult due to a shrinking and deteriorating individual market, as well as continual changes and uncertainty in federal operations, rules and guidance, including cost-sharing reduction subsidies,” one of the nation’s largest insurers, Anthem, said last week in explaining its decision to curtail its participation in the individual market in Nevada and Virginia.
Congress could reduce the uncertainty and stabilize insurance markets by providing money for the cost-sharing subsidies — a step…