Trade between the world's two largest economies comes into focus in Washington DC this week. Vice Premier Wang Yang will lead a Chinese delegation to the 27th session of the China-US Joint Commission on Commerce and Trade. The meeting comes amid worries about what will happen under the incoming Trump administration.

The combined total for U.S.-China trade was nearly 560 billion U.S. dollars in 2015.

And investment in each other's economies has been expanding, too. Chinese investment in the U.S. was a record 15 billion in 2015 and could be double that this year.

China-linked companies now directly employ 90,000 Americans. That's a 12% jump since last year.

Vice Premier Wang Yang will meet with U.S. Commerce Secretary Penny Pritzker and other top officials to talk about all aspects of the trade relationship-with a special focus on agriculture. There will also be talks on the long-negotiated bi-lateral investment treaty and a further opening up of both the U.S. and Chinese markets.

But the backdrop to these talks is a troubling one. U.S. President-elect Donald Trump talked on the campaign trail of an unfair relationship when it comes to trade with China. He pledged to renegotiate trade deals.

And a report last week from the U.S.-China Economic and Security Review Commission recommended that U.S. lawmakers impose restrictions on Chinese state-owned enterprises buying US companies. Beijing sharply criticized the report saying it was based on "Prejudices and stereotypes."   

And while negotiations will continue in Washington this week, the outgoing Obama administration will not be able to guarantee that its pledges will be honored after Obama leaves office.

Hence, US-China ties are at what Chinese President Xi Jinping called "a hinge moment." The question is which way will the door swing?