President Obama intends to nominate Sen. Max Baucus, D-Mont., as ambassador to China, Democratic officials said Wednesday, tapping a lawmaker well-versed in trade issues to fill one of the nation's most sensitive diplomatic posts.

At the same time, the move could help Democrats secure a key Senate seat ahead of the 2014 midterms.

If confirmed by the Senate, Baucus would replace Ambassador Gary Locke, who announced last month he was stepping down.

An announcement of Baucus' appointment is expected as early as Thursday.

In April, Baucus drew the ire of Democrats when he openly expressed fear about the rollout of ObamaCare. "I just see a huge train wreck coming down," he said.

Under state law, Democratic Gov. Steve Bullock has the authority to name a Senate successor to serve until the election, and speculation immediately turned to a fellow Democrat, Lt. Gov. John Walsh, already a candidate for a full term.

Baucus, 72, sidestepped questions about the ambassadorship when asked in the Capitol. "It's not for me to comment on... This happens every once in a while. Names get floated around."

There was no immediate comment from the White House on the disclosure, which was made by officials who spoke on condition of anonymity because they were not authorized to discuss the nomination publicly before a formal announcement.

Kathy Weber, a spokeswoman in Baucus' office, declined to confirm the move but said, "Max has given his life to public service and when asked to serve he takes that request very seriously."

With Democrats struggling to retain their majority in the 2014 elections, Baucus' announced retirement had turned the state into a challenging one for the party. Obama lost the state in 2012 to Republican Mitt Romney by 13 points.

First-term Republican Rep. Steve Daines already has announced his candidacy for the seat.

The National Republican Senatorial Committee immediately denounced the speculated China move, calling it a "back room deal" aimed at helping Democrats hold the seat.

"It reminds folks exactly what's wrong with Washington," Brad Dayspring, the committee's communications director, said in a statement Wednesday. "It is slick, and voters (especially in Montana) don't like Washington favoritism, and certainly don't like secretive deals that don't pass the smell test."

Inside the Senate, Baucus' appointment would create a vacancy atop the Senate Committee on Finance that Democrats would fill. Sen. Jay Rockefeller of West Virginia is immediately behind Baucus in seniority and ordinarily would ascend to the chairmanship but has announced he intends to retire at the end of next year. Sen. Ron Wyden of Oregon is next in line in seniority.

In comments to reporters, Rockefeller indicated he would not seek to claim the spot, saying it would be good if Wyden succeeded Baucus. "I want that committee to be a little more aggressive and he will be," he said.

Obama is in search of a new top diplomat in Beijing as he executes a so-called Asia pivot in U.S. foreign policy to more directly counter China after the wars in Iraq and Afghanistan.

The relationship between the two nations has grown more troubled in recent weeks, with Chinese authorities unilaterally declaring an air defense zone over disputed islands in the East China Sea. The United States subsequently flew a pair of B-52 bombers through the space last month without incident, and Vice President Joe Biden sought to calm matters on his recent trip through Asia.

Baucus was first elected to the Senate in 1978 and since early 2007 has been chairman of the Senate Finance Committee, which has jurisdiction over taxes, trade, health care and more.

On some key issues, he has pursued a more moderate approach than some fellow Democrats would prefer, a reminder that he hails from a rural, Western state with a history of electing Republicans as well as Democrats to top political office.

Shortly after becoming chairman, he led the opposition to then-President George W. Bush's proposal to privatize Social Security.

Two years later, with Obama in the White House, he struggled for months to assemble bipartisan backing for health care legislation in 2009 to the growing impatience of fellow Democrats. He managed to gain one Republican vote for legislation that cleared committee, but the final bill was thoroughly partisan.

As committee chairman, Baucus has pressed both Democratic and Republican administrations to take a harder line against what he says are unfair Chinese trade practices. The country has the largest trade surplus of any nation with the U.S. and American manufacturers claim it is manipulating its currency to maintain that imbalance.

If Baucus were to become the nation's next ambassador to China, he'd be following in the footsteps of his mentor, the late Montana Sen. Mike Mansfield, who ended his long political career by serving about 12 years as U.S. ambassador to Japan. A Baucus adviser told Fox News on Wednesday that the senator could be interested in similarly capping his own career as a leading American figure in U.S.-Asia relations.