WASHINGTON — U.S. and Chinese negotiators are holding high-level talks aimed at settling a six-month trade war that has weakened both sides, shaken financial markets and clouded the outlook for the global economy.

Yet the odds seem stacked against any substantive resolution this week to the standoff between the world’s two biggest economies. Perhaps the best that might be hoped for, analysts say, is for the two sides to agree to keep talking.

As the U.S. and Chinese delegations met Wednesday for the start of two days of talks, U.S. Trade Representative Robert Lighthizer welcomed a Chinese team led by Vice Premier Liu He. Lighthizer bantered lightheartedly about last year’s dinner meeting between Presidents Donald Trump and Xi Jinping in Buenos Aires, Argentina.

The differences between Beijing and Washington are vast. The United States is essentially demanding that China downsize its economic aspiration to become a supreme world leader in such fields as robotics and electric cars.

“A comprehensive deal that fundamentally changes their system — I don’t think that’s possible,” said Christopher Adams, a former U.S. trade official specializing in China and now a senior adviser at the law firm Covington.