WASHINGTON (Reuters) - Stephen Miran, President Donald Trump's chief economic advisor, looks set to clear a key hurdle in the U.S. Senate on Wednesday as Republicans rush through his nomination to be the Federal Reserve's newest governor, but lawmakers said getting him in place in time to vote on interest rates next week would be a long shot.

"I think that would be very challenging," Senator Cynthia Lummis, a Wyoming Republican on the Senate Banking Committee, said about the logistics of Miran getting confirmed by the Fed's September 16-17 rate-setting meeting. "Even rolling out the new process is going to be taking a lot of time," she said, referencing a potential change to aspects of the nominations process that Republicans are pursuing.

The banking committee is expected to vote on Wednesday to advance Miran's nomination for consideration by the full Senate, and despite expected unified opposition from Democrats the 13-11 Republican majority is expected to carry the vote.

And while Republican enthusiasm for Trump's nominee and their 53-47 control of the Senate means Miran's confirmation is likely, it's unclear how quickly a vote by the full Senate could be scheduled, due to the chamber's complex rules.

"I don't whip their side, but I'd be a little shocked," Senator Brian Schatz, a Hawaii Democrat, said about the logistics of Miran to be confirmed by the full Senate by Tuesday, when the Fed starts its two-day meeting. Fed policymakers hold their official vote to set rates on Wednesday, usually before noon.

A Senate Republican aide familiar with the confirmation process said the earliest possibility for Miran's confirmation is Monday.

Once confirmed by the Senate, Trump needs to sign the commission, and the Fed needs to swear Miran in. 

The fastest time in recent history from Senate confirmation to Fed swearing in is four business days. 

"They're gonna have to jump through a lot of hoops because we have a relatively full calendar as it stands," said Senator Thom Tillis, a North Carolina Republican on the banking committee, who confirmed he will support Miran's nomination for the fill-in term, "So this will be a very busy week, it'd be tight."

Trump has railed all year at Fed Chair Jerome Powell to lower interest rates, and installing Miran would be his first chance this term to put a like-minded voice at the central bank's policy-setting table. Two Fed governors - Michelle Bowman and Christopher Waller - appointed by Trump during his first term called for a rate cut in July and dissented when the majority voted to hold the policy rate steady in its current 4.25%-to-4.50% range. 

Many Fed policymakers, including Powell, have signaled a willingness to lower interest rates at the upcoming meeting given the weakening job market, a trend underscored on Tuesday in preliminary revisions to earlier employment data showing the job market was cooling fast even before Trump started his current term and began ratcheting up tariffs. 

Trump has pushed for far faster and steeper interest rate reductions.

Miran at last week's hearing did not say if he felt interest rates should come down, though he did say he feels inflation is headed downward and that tariffs won't reverse that trend, an argument that some Fed policymakers have used to help make the case for easier monetary policy. 

Miran said he planned to keep his job at the White House, taking unpaid leave rather than resigning as he serves a Fed governor term that expires at the end of January.  

Senator Elizabeth Warren from Massachusetts, the top Democrat on Senate banking committee, said that arrangement is disqualifying.

"He intends to hold on to an option of his old job in the White House, and that is the most non-independent nominee I have ever seen," she said. 

Republicans did not signal any discomfort with the idea and are moving forward with Miran's nomination process. 

Republicans plan to change Senate rules to allow some presidential nominees to be voted on as a group, fast-tracking votes that are currently held individually. The change could be debated as soon as early next week and comes as the Senate considers other pressing business, including the annual defense appropriations bill.

Senator John Cornyn, a Texas Republican, deferred questions on confirmation timing to his party's leadership.

"It's going to be an action-packed couple of weeks, and I don't know whether there's time for that," he said. "It's above my pay grade."