Baucus pushed for China's inclusion in the World Trade Organization in 2001, an important step in its integration in the world economy. Since then China has emerged as world's second-largest economy after America's, and Washington's second-largest trading partner. Two-way trade is projected to reach $558 billion in 2013.
China's record on its WTO obligations is mixed, and trade with the U.S. is skewed heavily in China's favor.
As chairman of the Senate Finance Committee, which oversees trade, Baucus has sponsored legislation to punish China for undervaluing its currency to benefit its exporters. The measure never made it into law. He's also criticized China for shutting out U.S. beef imports. But he's remained a strong advocate of expanding trade.
"The economic and financial relationship with China is crucial," said Cheng Li, a China expert at the Brookings Institution, a Washington think tank. "If that part of the relationship is healthy it can spill over and have a positive effect in other areas. But if it's jeopardized it can adversely affect other areas, including on security."
He expected China's leaders to welcome Baucus' appointment, given his stature as a six-term senator and close ties with Obama.
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China's Global Times newspaper, which is affiliated with the ruling party, said Baucus' experience made him a good pick for the job.
"We hope and believe that Mr. Baucus can bring his Capitol Hill experience and personal relationship with the president to use in furthering U.S.-China trade ties and the building of a new type of major state-to-state relationship," the paper said, using Beijing's buzzword for its desire to be treated by Washington as an equal.
The current ambassador is Gary Locke, a former commerce secretary.
As the first Chinese-American ambassador to Beijing, Locke has been a well-known and generally well-liked figure in China. He created a buzz among ordinary Chinese even before he arrived in Beijing after he was photographed wearing a backpack and trying to use a coupon to buy coffee at Seattle's airport.
Many Chinese Internet users pointed out the contrast with Chinese bureaucrats, who routinely have aides carry their bags and attend to minor tasks.
Locke has navigated choppy waters in the relationship, notably when dissident lawyer Chen Guangcheng in 2012 sought refuge in the U.S. Embassy on the eve of high-level U.S.-China talks in Beijing. China subsequently allowed Chen to leave for New York, and the talks proceeded.
Given the prickly state of the U.S.-China relationship, Bonnie Glaser, a China expert at the Center for Strategic and International Studies, voiced surprise that Obama did not select an envoy with more clout on security issues.
She said Baucus' nomination reflected the president's tendency to focus on the economic aspects of the relationship with China as he tries to boost exports and reduce unemployment at home.
His administration wants to "level the playing field" for American companies: curb cybercrime and theft of intellectual property and improve market access, particularly in the heavily restricted services sector. The U.S. has welcomed China's intent to open state-dominated industries wider to private competition and ease limits on foreign investment.
Erin Ennis, vice president of the U.S.-China Business Council, said a priority for Baucus should be to negotiate a strong bilateral investment treaty.