Facing a midnight Friday deadline, the House is expected to vote Thursday on a short-term spending bill to fund the government through Jan. 19.

The bill unveiled Thursday morning contains $2.85 billion for the popular Children's Health Insurance Program and $750 million for diabetes programs and community health centers.

The bill also extends the foreign surveillance warrant program, known as FISA 702, and includes an extra $4.7 billion to fund ship repair and missile defense programs at the Department of Defense.

The continuing resolution is "clean," meaning it does not contain provisions that are contentious enough to threaten the bill's eventual passage. The federal government officially runs out of funding at midnight Friday, making this a must-pass measure.

"We're just bringing a clean, what we call vanilla CR — no games, no sneaky things. Just a continuing resolution to get us through this moment to get us into next year," House Speaker Paul Ryan told CNBC's "Squawk Box." "It's as clean and simple as possible."

That may not be entirely true, however. Buried on the last page is what's called a "pay-go" waiver: language that would allow President Donald Trump to immediately sign the tax bill Republicans' passed Thursday without running afoul of rules that prohibit the government from enacting big new expenditures, such as the GOP tax cuts, unless there is money in the current year's budget to pay for them.

Without such a waiver, Trump will likely have to wait two more weeks and sign the tax bill in January, when Republicans would have another 12 months to figure out how to make the expensive tax cuts conform to pay-go rules.

It remained unclear Thursday how exactly Ryan intended to pass the CR in the House — whether by Republican votes only or with support from Democrats. It was likewise unclear exactly what the Senate would do if the House passes the measure — offer a separate spending package or just vote to send the House CR to Trump's desk before midnight on Friday.

The pay-go language could also complicate the CR's chances of passing the Senate. Budget hawk Sen. Rand Paul was quick to signal his opposition to the idea of waiving longstanding pay-go rules merely in order to give the president a chance to say he fulfilled his promise to sign the tax bill by Christmas.

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The House is expected to adjourn for the holidays following passage of the spending bill.