(BBC) - In California's Livermore Valley, about an hour east of San Francisco, some 5,000 cases of Wente Vineyards wine are waiting in a warehouse, their journey to China suddenly suspended.

The bottles have been caught up in a larger trade dispute, in which the US and China have exchanged threats to impose tariffs on billions of dollars worth of products, including American wine.

Wine might seem like a bit player in the fight, which revolves around American concerns about Chinese state subsidies and rules they say pressure US technology firms and car-makers to hand over intellectual property.

But as the two countries settle down to negotiate, the industry offers a glimpse of what's at stake in the confrontation, which has led to unease on financial markets and prompted warnings of a trade war.