A farmer verifies that his equipment is dropping seeds at the appropriate depth as he plants a cornfield outside Henry, Ill.

U.S. and China's "substantial" deal is already looking hazy, especially regarding China's promise to hike its purchase of agricultural products, The Wall Street Journal reported Wednesday.

Uncertainty reigns over China's commitment to buy more farm products from the U.S. Reports say details are lacking over time frame and amount of purchases that were promised.

During trade talks last week, President Donald Trump said China agreed to purchase about $40 billion to $50 billion worth of U.S. agricultural products "in less than two years." However, it is unclear what the U.S. might have to concede in return for this aspect of the deal, and if tariffs slated for December could be used as leverage.

The U.S. is schedule to impose a new 15% tariffs on more than $150 billion in goods on Dec. 15.