Health insurer Humana is withdrawing completely from the Obamacare marketplaces in 2018, citing steep financial losses from patients in the individual market.

The company announced the move Tuesday afternoon, becoming the first major insurer to announce its strategy for next year.

Humana covers just a small sliver of Obamacare enrollees — about 150,000 — but its exit bodes poorly for the marketplaces next year as insurers consider whether they can be profitable there. Insurers are also uncertain about what the marketplaces might look like next year, as congressional Republicans seek to repeal and replace the law but haven't decided exactly how to handle it.

Like a number of other insurers, Humana had already dramatically scaled back its participation in the marketplaces set up under the Affordable Care Act. It is selling plans in just 11 states this year, compared with 19 states in 2016.

The company said it tried to take actions to stabilize its individual insurance market, but has decided its risk pool is too unbalanced now that the 2017 enrollment season is over.

"Therefore, the company has decided that it cannot continue to offer this coverage for 2018," the company said.

Shortly after the announcement, President Trump tweeted: "Obamacare continues to fail. Humana to pull out in 2018. Will repeal, replace & save healthcare for ALL Americans."

The announcement comes the same day as Humana and Aetna called off a planned merger, after a federal judge blocked the two major insurers from combining and further consolidating the insurance industry, citing antitrust concerns.

Humana is the second major insurer to withdraw from the marketplaces, following a decision last year by United Healthcare to stop selling on the individual market due to heavy losses.