SYDNEY, Nov 18 (Reuters) - Top Australian wine producer Treasury Wine Estates Ltd said on Thursday it will buy the Napa Valley's Frank Family Vineyards for $315 million, building its high-end U.S. offering as it resets its strategy in the wake of hefty new tariffs in China.

Treasury, one of the world's biggest listed wine companies, has been unwinding its exposure to China since its biggest export market imposed tariffs of up to 176% this year, citing complaints about "dumping", selling cheaply to win marketshare.

The owner of the Penfolds label has meanwhile been recalibrating its business in the United States, another core market, away from low-margin "commercial" wine and towards higher-end, more profitable product.

The Frank Family purchase, which Treasury said it would pay for partly with proceeds from lower-end U.S asset sales, would improve its standing in the luxury wine market, particularly chardonnay.

"The acquisition ... represents an outstanding complementary addition to the Treasury Americas brand portfolio and is another important step towards our ambition of becoming the premium wine market leader in the Americas," Treasury CEO Tim Ford said in a statement.

"This is a rare opportunity to acquire a luxury brand and portfolio of wines that consumers enjoy and connect with."

A Frank Family Vineyards representative did not immediately respond to a Reuters email out of business hours.

Treasury shares were 2% higher in mid-session trading, against a slight gain in the broader market. (Reporting by Byron Kaye; editing by Richard Pullin)