Aetna was responding to a question from the Justice Department when it said a blocked merger with Humana could force it to quit Obamacare.

The letter, obtained by the Washington Examiner's Tim Carney, casts doubt on reports that Aetna was threatening to pull out of the Affordable Care Act marketplaces in retribution against the federal government for trying to block its proposed merger with Humana.

In the June 30 letter, the Justice Department asked Aetna to explain how blocking the merger would affect the company's "participation on the public exchanges related to the Affordable Care Act" and submit related documents.

Aetna responded with a letter saying it would experience "negative financial impact" if Justice were to try to block the merger, making it hard to continue selling Obamacare plans. Aetna CEO Mark Bertolini indicated his company needs to be allowed to merge with Humana to stay on a strong financial footing.

The Aetna letter, first reported Wednesday by the Huffington Post, made it appear as though the company was threatening to withdraw from the exchanges as retribution. The company had announced earlier in the week that it would no longer offer Obamacare plans in all but four states.

But according to the letter from the Justice Department, Aetna was merely responding to a request that it explain how it would fare in the Obamacare marketplaces should the merger be blocked.

Department of Health and Human Services spokesman Benjamin Wakana told the Washington Examiner he didn't have a comment on the letter.

The Justice Department has sued to block two major health insurance mergers that would reduce the number of big insurers from five to three.