Some of the bullish positions included call options on the Xtrackers Harvest CSI 300 China A-Shares ETF with a $27 strike price - some 6% higher than where the fund trades today - set to expire Friday.

The iShares Trust-China Large-Cap ETF also sport multiple lines of at-money and upside calls with sizeable open interest, including almost 100,000 contracts at the 29.85 strike. The ETF was trading at $27.28 on Wednesday.

Other large China-focused ETFs, including the iShares MSCI China ETF, KraneShares CSI China Internet ETF, also showed upbeat options activity, according to Trade Alert data.

"It certainly seems that there is generally bullish positioning ahead of the meeting," said Steve Sosnick, chief strategist at Interactive Brokers, noting that the positions had been built up over several days. "The open interest in options expiring Friday is heavily skewed to the upside."

While some of the upside positioning may be tied to a rally in the broader equity market - including a Tuesday surge that saw the S&P 500 rise 1.9% on bets that the Federal Reserve is done hiking interest rates - investors are also likely speculating on a positive outcome from the meeting between Biden and Xi, Sosnick said.

"The bullish positioning in ASHR and FXI is almost certainly the result of pre-meeting enthusiasm since it is highly biased to near-term upside calls and the positioning occurred prior to yesterday's run-up," Sosnick said.

Biden and Xi arrived in San Francisco on Tuesday, where they were set to hold their meeting on the sidelines the Asia-Pacific Economic Cooperation (APEC) summit. The meeting is set for 2 p.m. ET (1900 GMT).

Investors' nascent enthusiasm for Chinese stocks is at odds with how these ETF's have performed this year. The largest China-linked ETFs are down anywhere between 3% to 9% for the year. Meanwhile the S&P 500 is up nearly 18%. Fund managers in the November BofA Global Research survey named shorting China equities as the market's second "most crowded" trade. Daniel Kirsch, head of options at Piper Sandler, said recent bullish options flows into KWEB may be to do with a combination of enthusiasm ahead of the Biden-Xi meeting as well as results from Chinese e-commerce companies JD.com and Alibaba. On Wednesday, JD.com reported a surge in third-quarter profit, while Alibaba results are expected after the close of trading. "People are looking for areas that could be catching up (to the rally in broader markets)," Kirsch said.

(Reporting by Saqib Iqbal Ahmed; Additional reporting by Suzanne McGee; Editing by Ira Iosebashvili and Jonathan Oatis)

By Saqib Iqbal Ahmed