By Caroline Humer

NEW YORK (Reuters) - A U.S. government health agency on Thursday said that it was considering new rules to prevent healthcare providers or related groups from steering patients into Obamacare individual insurance plans instead of Medicare or Medicaid in order to receive higher payments for medical services.

The Centers for Medicare & Medicaid Services on Thursday said it is seeking public comment and considering rules including prohibiting or limiting premium payments or cost-sharing for the individual marketplace plans, monetary penalties and limits on such payments.

It also sent a letter to dialysis centers that are part of Medicare informing them of these plans.

"It is improper to influence people away from Medicare or Medicaid coverage for the purpose of financial gain," Shantanu Agrawal, CMS Deputy Administrator and Director of the Center for Program Integrity, said in a statement.

Three of the largest U.S. health insurers have raised the issue of third-party payments in recent months, including UnitedHealth Group Inc, Anthem Inc and Aetna Inc.

UnitedHealth and Aetna have decided in 2017 to largely exit the government-run online marketplaces that sell these subsidized plans created under President Barack Obama's national healthcare reform law.

Under Obamacare, individual plans offered by the insurers generally pay doctors and other medical groups more than Medicare and Medicaid for their medical services and may cover different drugs and procedures.

UnitedHealth filed a lawsuit against American Renal Associates Holdings earlier this summer that has to do with payments for dialysis through its exchange plans.

Aetna said during an Aug. 2 conference call with investors that third-party payers steering patients to the individual market had contributed to an unhealthy mix of customers in its individual plans sold on the exchanges.

(Reporting by Caroline Humer, editing by G Crosse)