Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellDemocratic senator to party: 'A little message discipline wouldn't kill us' House to vote on resolution affirming peaceful transition of power Republican lawyers brush off Trump's election comments MORE (R-Ky.) hit a snag on Thursday as he tries to confirm a former top staffer to a Treasury Department post: An objection from fellow Kentucky Republican Sen. Rand Paul Randal (Rand) Howard PaulRon Paul hospitalized in Texas The Hill's Morning Report - Sponsored by Facebook - Trump previews SCOTUS nominee as 'totally brilliant' Rand Paul says he can't judge 'guilt or innocence' in Breonna Taylor case MORE.

The Senate was expected to take up Brian McGuire's nomination to be deputy undersecretary at the Treasury Department on Thursday. McGuire previously served as McConnell's chief of staff.

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But a procedural vote expected around noon was abruptly called off. Senate staffers subsequently announced that there would be no roll call votes in the Senate on Thursday.

GOP senators said after a closed-door lunch that Paul was objecting to holding a vote on McGuire on Thursday.

McConnell filed cloture on McGuire's nomination on Wednesday, teeing it up for floor action. But under Senate rules the soonest it could come up for a vote was Friday without the consent of every senator — giving Paul an opening to delay the nomination.

Paul's objection is only a temporary setback. Instead of voting on his nomination on Thursday, the Senate will now hold a procedural vote on Monday evening.

McConnell, who is running for reelection, introduced McGuire at his hearing before the Senate Finance Committee, saying he was "deeply saddened" when McGuire went into the private sector.

"I'm really proud of him. I think he will make a fabulous addition to the Treasury Department. ... This is a top-flight nominee. I think the president was wise to select him," McConnell said.

A spokesman for Paul said that the decision to temporary hold up McGuire's nomination wasn't personal, but that the Treasury Department has "been less than responsive" in negotiations over tax treaties.

“For many years, Senator Paul has advocated to amend tax treaties to protect the privacy of American citizens. Recently, the Department of Treasury has been less than responsive, and Senator Paul has decided to vote against some of their nominees. There is no animosity toward this specific nominee," the spokesman said.

It's the latest twist after McConnell and Paul split over four tax treaties that the Senate approved in July. McConnell backed the measures, which had been held in limbo by Paul.

The two traded shots at each other on the Senate floor as the chamber debated, and ultimately passed, the treaties.

Paul, at the time, accused the GOP leader of undercutting his efforts to put additional privacy protections in the treaties.

“This process has been severely damaged and short-circuited by the Republican leader, choosing to push this forward and destroy the negotiations that we were having at the time,” Paul said. McConnell hit back from the Senate floor, saying that he was "a patient man, but my patience is not inexhaustible." McConnell hit back from the Senate floor, saying that he was "a patient man, but my patience is not inexhaustible."

“I don’t know why the senator believes he was close to a breakthrough after his years of effort,” McConnell added. “Hope springs eternal, I suppose.”

— updated at 3:20 p.m.