The response to an information request contradicted the administration's public testimony and raised concerns that it may be trying to evade oversight.
The move by Representative Haley Stevens, a Michigan Democrat who is running for Senate, does not have the support of her party's leaders and is all but certain to fail.
Senate Republicans plan to offer a proposal that would create a new payment for people with bare-bones health coverage, clashing with Democrats who are pressing for an extension of existing tax credits.
