By Krista Hughes and David Brunnstrom WASHINGTON (Reuters) - The United States and China have exchanged revised offers for a proposed investment treaty, a spokeswoman for the U.S. Trade Representative said, in the lead-up to Chinese President Xi Jinping's visit to the White House next week. China, which has more restrictions on foreign investment than the United States, is in talks with Washington to reduce the scope of so-called negative lists of sectors closed to the other side's investors. The USTR spokeswoman said revised negative list offers were exchanged at talks in Washington last week. Business groups are hoping for news on the bilateral investment treaty (BIT) during Xi's visit to the United States, which is expected to start on the West Coast next Monday and include talks with President Barack Obama later in the week. "The United States continues to review China’s revised negative list and assess next steps in the negotiations," the USTR spokeswoman said in an emailed statement late on Monday. "In order to conclude the BIT negotiations successfully, the two sides will need to reach agreement on a high standard treaty text and a Chinese negative list that is limited, narrow, and represents a substantial liberalization of the Chinese investment market." China on its part complains that the United States has singled out Chinese investors for national security reviews. The sides exchanged initial lists in June. On Tuesday, a group of 94 CEO's of some of America's biggest firms signed a letter to Xi and Obama calling for the rapid conclusion of "a meaningful and high-standard" bilateral investment treaty, saying they hoped "significant" progress could be made during Xi's visit. "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,” they said. The CEOs included Tim Cook of Apple, Warren Buffett of Berkshire Hathaway, Rex Tillerson of ExxonMobil, Jeffrey Immelt of General Electric, Muhtar Kent of Coca Cola, Mark Fields of Ford, Doug McMillon of Walmart and Mark Zuckerberg of Facebook. U.S. investors hope that a treaty will give them increased access to China's many state-dominated industries, from financial services to telecommunications. Last month, the American Chamber of Commerce in China said turmoil in China's stock markets should encourage Beijing to open the economy more quickly to foreign services companies, including banks, and that it hoped to see progress during Xi's visit. Foreign business leaders have said Chinese regulations intended to bolster national security have called into question China's commitments to market reforms and could further restrict foreign access to sensitive sectors. Nonetheless, some experts say factions in China would like to use the external pressure of the BIT to hasten reforms. (Reporting by Krista Hughes anbd David Brunnstrom; Editing by Meredith Mazzilli and Andrew Hay)