Chinese President Xi Jinping (right) with Zeng Peiyan, director of the China International Economic Exchange Center, during a meeting between U.S. business leaders and former senior officials at the Great Hall of the People, Sept. 17, 2015, in Beijing. Lintao Zhang/Pool/Getty Images

Ahead of Chinese President Xi Jinping's scheduled visit to the United States next week, China has landed a milestone contract to help build a high-speed railway from Las Vegas to Los Angeles. A first-of-its kind agreement on cyberwarfare also is possible. But what of an accord for which U.S. investors have spent years pining to afford American companies protections and leeway to put more money into the U.S.'s second largest trading partner?

Ongoing negotiations over a U.S.-China bilateral investment treaty (or BIT) began in 2008, and outside experts have expressed optimism those talks are, at last, headed toward a positive conclusion. Last month, Malcolm Lee, a senior fellow at the Brookings Institution, and a veteran of both the White House's National Economic Council and Microsoft, surmised Xi's visit with President Obama "would be a good time to announce liberalizing measures."

China's state-run Xinhua news agency Friday reported the visit "will push forward the negotiation for a bilateral investment treaty between China and the United States," according to observations by a scholar with the Chinese Academy of International Trade and Economic Cooperation.

U.S. CEOs, however, reportedly have been less sanguine in recent days. “We’ve seen incremental progress but not yet substantial progress,” Myron Brilliant, international vice president of the U.S. Chamber of Commerce, told the Wall Street Journal in a Friday report. “We made it clear, it’s not good enough.”

China's latest offer "still lists between 35 and 40 sectors off limits to foreign investors," Brilliant, a member of a delegation that recently spent two days in talks with Chinese counterparts, said in the Journal interview. The delegation also included U.S. CEOs from the tech, steel and pharmaceutical sectors.

Last Tuesday, 94 U.S. CEOs -- including Apple's Tim Cook, Walmart's Doug McMillon and Coca Cola's Muhtar Kent -- called on Xi and Obama to make "significant" progress in the treaty talks, Reuters reported.

"A high-standard BIT -- with clear provisions providing equal treatment to each country’s investors and a short list of exceptions -- is one of the key items that could make an immediate and tangible impact for both of our economies," the CEOs said in a letter to the leaders of both countries.