China says it welcomes a planned visit by U.S. Treasury Secretary Steve Mnuchin next week amid trade tensions. Both countries have proposed tariffs of $50 billion on each other's products. That includes steel and aluminum from China and wine, almonds and cherries from California.

Brian Kuehl with the bipartisan, nonprofit group Farmers for Free Trade says some California farmers are already feeling the impacts.

"We know anecdotally a number of farmers have already lost contracts for wine, as an example,” says Kuehl. “California obviously exports a huge amount of wine, a lot of it destined for China. We understand that some of those wine contracts have already been throttled back."

Kuehl says, for a lot of farmers, the impact hasn't been felt yet.

"And by that I mean there's discussion of additional tariffs that would hit soy, it would hit beef, it would hit cotton,” says Kuehl. “So if you're in one of those markets that maybe hasn't been hit so far, I think there's nervous anticipation about where this is all headed."

He says once you lose an export market it doesn't come back immediately.

"So if you're an apple grower and you’re exporting your apples to China and you lose a contract to sell your apples to China, you may not see that come back for a year, two years, five years after these tariffs go away,” says Kuehl. “So this can be a very long term impact on U.S. agriculture."

Experts say the proposed tariffs would likely hurt California's tree nut growers more than its wine producers because a larger proportion of almonds and pistachios are exported.

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