BEIJING, Dec. 12 -- The 17th round of China-U.S. investment treaty negotiations kicked off in Beijing on Friday, the China Commerce Ministry said.

The two sides will step up discussions on "core issues of the treaty text" in an effort to complete the talks during the five-day negotiations, the ministry said in a brief statement on its website, without providing further details.

Talks over the treaty began in 2008 as the two countries sought to lift mutual investment, which only accounted for a tiny share of their overseas investment.

The two sides have held six rounds of talks this year and plan to start substantive negotiations on the "negative list", namely, sectors and items barred to investment, early next year.