The two recent U.S. WTO complaints against China are here:
China - Electronic Payment Services (DS413)
China - AD/CVDs on Electrical Steel (DS414)
President Obama had this to say on the issue of trade complaints against China in reponse to a question yesterday at a town hall:
MR. HARWOOD: China. A very quick way to improve the competiveness of U.S. exports would be if the value of China’s currency rises. Is it time for you to be tougher than you have been so far on pressing the Chinese?
THE PRESIDENT: This is a real problem. And I want to just give everybody some background on this. China -- its currency is valued lower than market conditions would say it should be. And what that means is essentially that they can sell stuff cheaper here, and our stuff when we try to sell there is more expensive. So it gives them an advantage in trade.
What we’ve said to them is you need to let your currency rise in accordance to the fact that your economy is rising, you're getting wealthier, you’re exporting a lot. There should be an adjustment there based on market conditions. They have said yes in theory, but in fact they have not done everything that needs to be done. We are going to continue to insist that on this issue and on all trade issues between us and China, that it’s a two-way street.
Look, it’s good for us that China does well, in the sense that, first of all, having millions of people get out of poverty is a good thing for the world. It makes them more stable. It buys them into a world economy that can reduce tensions and allow our businesses to thrive. It’s a huge market where we should be able to export a lot of goods. Eventually, I want some of those nice monogrammed glass things to be in Shanghai and Beijing. (Laughter.) But it’s got to be fair. Our trade relationship has to be fair. You can’t just sell to us and we can’t sell to you.
And so we have been bringing more actions against China before the World Trade Organization. We are going to enforce our trade laws much more effectively than we have in the past -- not because I’m anti-trade. I’m pro-trade. I just want to make sure that trade is good for American businesses and American workers. And over the last several years, it hasn’t always been.
Of note in DS414 is that Buy America and the "stimulus" play a role in the complaint:
In particular, China's countervailing and anti-dumping measures on GOES from the United
States appear to be inconsistent with the following provisions of the GATT 1994, the SCM
Agreement and the AD Agreement....
Articles 10 and 19 of the SCM Agreement, because China improperly determined that
government purchases under US Buy American Laws conferred a "benefit"....
Article 22.2(iii) of the SCM Agreement, because China included in its countervailing duty
investigation the American Recovery and Reinvestment Act of 2009 ("Recovery Act") and laws of the various US states dealing with the government purchase of goods.
The stimulus claim seems to be a procedural one; I'm not sure what the exact substance of the Buy America related claim is.