The head of Bayer's crop science division told Reuters his company could even benefit if U.S. farmers switched to grow more corn to avoid barriers to the soy trade imposed by China in response to U.S. tariffs on Chinese products.

The combination of Bayer-Monsanto has a much bigger market share in corn seeds and related crop protection products than in the soy market, so it could capture more of that growth.

"The big unknown next year will be how U.S. farmers react to the Chinese-U.S. trade war," Liam Condon said on the sidelines of a news conference at the division's headquarters in Monheim, Germany.

"There could even be a positive development, when U.S. farmers for instance grow less soy and more corn," he said, adding China mainly relied on the United States for soy imports and less for corn.

The Monsanto takeover made Bayer the world's largest maker of seeds and pesticides, ahead of DowDuPont Corteva Agriscience, Syngenta and BASF.

China said on Tuesday it had no choice but to retaliate against new U.S. trade tariffs, raising the risk that U.S. President Donald Trump could soon impose duties on virtually all of the Chinese goods that America buys.

U.S. soybean farmers have seen crop prices fall and export markets shrink after Trump's tariffs triggered retaliation from buyers.

"What's safe to assume, other things being equal, is that more Brazilian soy will go to China, and much less from the U.S to China," Condon said, adding that U.S. soy might head to Europe if Brazilian trade focussed on its new Chinese market.

"The total sum of produce will not change significantly but the trade flow might shift," he added.

The United States and Brazil are major markets for Bayer Crop Science, with the former generating profits mainly in the first half of the year and the latter in the second.

Bayer this month cut its earnings forecast due to delays to its $63 billion takeover of Monsanto, and said sales of its consumer care products fell, hitting its shares, already reeling from a legal battle over the weed killer Roundup.

(Editing by Edmund Blair)

By Ludwig Burger and Patricia Weiss