WASHINGTON: Bilateral investment talks between the United States and China “continue to be productive,” the US Trade Representative’s office said on Friday after the two sides exchanged new offers this week. A USTR spokeswoman said US and Chinese negotiators exchanged revised “negative lists” of sectors that would stay off-limits from foreign investment as they try to reach a deal for a bilateral investment treaty. “China will need to demonstrate the substantial liberalization of its investment market, ensure that US firms can compete on a level playing field, and address other key priorities to facilitate the progress and successful conclusion of a mutually beneficial and high standard BIT,” the USTR spokeswoman said in a statement. Obama administration officials and US companies have complained that China has over 100 sectors of its economy closed to US investment and that these must be narrowed substantially to reach a treaty deal.