“Today’s meeting was focused on how to build on the continued progress in reducing the uninsured rate and moving forward with policy solutions that will support a stable, affordable market for 2017 and beyond,” Clare Krusing, a spokeswoman for America’s Health Insurance Plans, the industry’s Washington lobby group, said in an e-mail.

Republicans have pointed to large premium increases for 2017 in many states as a sign of trouble with the law, and continue to advocate for its repeal. Enrollment season begins Nov. 1, a week before the U.S. presidential election.

In his letter, Obama said his administration was working on ways to boost enrollment among younger, healthier people, who are essential to balancing the risk of covering sicker, healthier people. The White House will hold a “Millennial Outreach and Engagement Summit” this month to increase youth enrollment in the insurance marketplaces.

“Since the remaining uninsured are disproportionately younger and healthier, signing them up improves the risk pool and consequently the affordability of coverage for all enrollees,” he wrote.

Executives from Aetna and UnitedHealth did not participate in the meeting. Humana CEO Bruce Broussard did attend, according to the White House. Anthem Inc., the largest for-profit insurer broadly participating in the program, said its chief executive officer, Joseph Swedish, was invited to attend but had a scheduling conflict. The companies involved in the meeting represented a wide range of insurers, including non-profit and for-profit firms, a White House official said.

A person familiar with the conversation who asked not to be identified discussing a private meeting said that insurers told Obama and White House officials that the government should crack down on people who try to wait until they get sick to sign up for coverage, among other moves that would stabilize the program and make it easier for plans to turn a profit.

“It’s important to the people and communities we serve to have access to affordable health care options,” said Scott Serota, CEO of the Blue Cross Blue Shield Association and a participant at the meeting. “To achieve this, the rules must encourage people to be continuously insured so they get the ongoing care they need. We continue to work with the administration toward this critical goal.”

The Affordable Care Act relies on privately run insurers to offer health plans that individuals can buy, often with government subsidies. About 11.1 million people were signed up for Obamacare plans at the end of March.

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