Story highlights The Senate and the House each passed their own version of a tax bill

Most of the work of the conference committee will happen in private negotiations

(CNN) Republicans have celebrated since Saturday the passage of their tax bill through the Senate, but on Monday night some key GOP members were thinking of another measure -- one to keep the federal government funded -- when they threatened to vote against a routine step to send the tax plan to a conference committee.

Senate Republicans passed their tax bill in the early hours of Saturday morning and now Republicans across the Capitol are bracing themselves for their next challenge: conference -- and even that step looked at least for a few moments Monday evening to be in jeopardy.

The House of Representatives formally voted 222-192 Monday night to go to conference committee on the tax bill, where it will work to iron out key differences between its bill and the Senate's. The House later Monday evening appointed the conferees, the select lawmakers tasked with trying to deliver the reconciled tax bill to President Donald Trump's desk before Christmas.

The office of House Speaker Paul Ryan, R-Wisconsin, said he had named as conferees GOP Reps. Kevin Brady of Texas, Devin Nunes of California, Peter Roskam of Illinois, Diane Black of Tennessee, Kristi Noem of South Dakota, Rob Bishop of Utah, Don Young of Alaska, Greg Walden of Oregon and John Shimkus of Illinois.

House Minority Leader Nancy Pelosi, D-California, announced her choices as Democratic Reps. Richard Neal of Massachusetts, Sander Levin of Michigan, Lloyd Doggett of Texas, Raúl Grijalva of Arizona and Kathy Castor of Florida.

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