Senator Max Baucus, a Democrat from Montana, will be appiointed ambassador to China. (Julia Schmalz/Bloomberg)

President Obama plans to nominate outgoing Sen. Max Baucus (D-Mont.) as the next U.S. ambassador to China.

The White House and Baucus declined to comment Wednesday on the pick, but Sen. Orrin G. Hatch (R-Utah) and several Senate aides and Baucus allies confirmed the decision.

Baucus, 72, stunned the political establishment this year when he announced that he wouldn’t seek reelection next year.

As chairman of the powerful Senate Finance Committee, Baucus played a key role in crafting Obama’s health-care law and was among the first Democrats to publicly worry about the law’s implementation — worries that were later found out to be justified.

Baucus also has expressed a desire for a significant overhaul of the nation’s tax code, something he and House Ways and Means Committee Chairman Dave Camp (R-Mich.) hoped to tackle this year, after decades of failure to do so. Baucus’s nomination would seemingly put that on hold.

Sen. John D. Rockefeller IV (W.Va.) is the second-ranking Democrat on the committee. He chairs the Commerce, Science and Transportation Committee and is also retiring after next year. Senate Energy Committee Chairman Ron Wyden (D-Ore.) is next in line on the panel and is seen as the all-but-certain successor to Baucus at Finance, considered the most powerful perch in the Senate.

The timing of Baucus’s departure for Beijing is unclear, but Republicans signaled Wednesday that the 35-year Senate veteran, who has a penchant for bipartisan deal-making that sometimes drove Democrats to anger, would face little obstacles in winning confirmation.

“He ought to be confirmed immediately,” Hatch, the ranking Republican on Baucus’s committee, said.

Politico first reported the news of Baucus’s pending nomination.

Wyden, notably, has been highly critical of the administration’s surveillance programs in recent months. The last big tax reform deal came in 1986, when another Oregonian, Republican Bob Packwood, chaired the committee. Trying to invoke Packwood’s bipartisan spirit, Baucus and Camp have hosted a series of lunches at the Irish Times, a Capitol Hill watering hole that was Packwood’s favorite haunt.

Baucus’s nomination plays a key role in the battle for control of the Senate.

With the vacancy, Montana Gov. Steve Bullock (D) will get to make the appointment for the final year of Baucus’s term, and Democrats were looking closely at the idea of Bullock appointing his lieutenant governor, John Walsh, who is already running to replace Baucus. Rep. Steve Daines is the leading Republican candidate.

China analysts welcomed the impending nomination of Baucus.

Kenneth Lieberthal, the national security director for Asia during the Clinton administration, said Baucus’s appointment could be a good choice because he understands trade issues well. The Obama administration was probably looking for “someone of stature, someone Chinese know has access to White House and understands politics at home,” he said.

“It’s important to nominate and extend a prominent figure like him,” said Michael Green, a former Asia adviser in the George W. Bush administration.

William Wan in Beijing contributed to this report.