"The talks will conclude. They have to," Baucus told CNBC's Martin Soong at the Boao Forum for Asia in the Hainan province of China. "U.S, China, we're so closely joined at the hip economically, we got to get this thing done."
"There's some feeling here maybe — by the end of April, maybe a little longer — but we'll get it done," Baucus said, noting that otherwise, U.S. stock markets and China's already slowing economy would be negatively impacted.
President Donald Trump has often compared his political success with the U.S. stock market, which has pushed higher over the last 10 years in the longest bull market in history. Meanwhile, official figures showed China's economy grew at its slowest pace last year since 1990, and authorities expect the rate to slow further this year.
For those reasons, Baucus said there is greater impetus for the U.S. to make a deal with China.
He also said the near-term fallout of nuclear talks between Trump and North Korean leader Kim Jong Un in late February should not be used as an example for how trade negotiations between the world's two largest economies might end.
The question for Beijing is whether Trump will live up to his side of the deal, said Baucus, who was the U.S. ambassador to China from 2014 to 2017 under President Barack Obama.
The Trump administration is also looking for ways to ensure enforcement on China's side.
A meeting between Trump and Chinese President Xi Jinping, originally expected for the end of this month, has been delayed.
For now, U.S. Trade Representative Robert Lighthizer and Treasury Secretary Steven Mnuchin are set to hold trade talks in Beijing beginning Thursday. The Chinese delegation under Vice Premier Liu He is expected to lead a team to the U.S. next week.