By Karl Plume

CHICAGO, Feb 4 (Reuters) - Global grains trader Archer-Daniels-Midland ADM.N is slashing costs and cutting staff to weather a commodity downturn made more challenging by uncertainty about U.S. biofuels policies and a brewing trade war, the company said on Tuesday.

ADM's difficulties follow an accounting scandal last year that forced the company to twice revise financial statements and triggered an ongoing federal investigation.

ADM on Tuesday posted its weakest fourth-quarter profit in six years and forecast what could be a third-straight annual earnings drop in 2025.

ADM said it is eliminating up to 700 jobs and aiming to cut up to $750 million in costs in the next three to five years, joining agribusiness rival Cargill in tightening its belt.

CEO Juan Luciano said it was difficult to predict how ADM's global trading business would fare if President Donald Trump's orders to raise tariffs on Canada, Mexico and China spark broad retaliation from the top three buyers of U.S. farm goods.

China launched limited tariffs on Tuesday in retaliation against sweeping new U.S. levies on Chinese goods. Beijing's tariffs did not include crops.

Trump suspended the tariffs on Canadian and Mexican goods for one month.

"Tariffs imposed by the U.S. government tend to have a slightly positive benefit to us," Luciano said, adding "the issue is the retaliatory measures."

ADM is on a short list of grain-trading companies that can benefit from such trade turmoil, he said.

If an overseas buyer curbs its imports of U.S. farm products, ADM could still supply that market with crops from other countries such as Brazil, although such disruptions can dent trading margins.

ADM flexed its global grain origination and distribution footprint in 2018 when China slashed its U.S. soybean purchases, prompting the company to tap its Brazilian supply chain to supply that country.

Meanwhile, ADM and other crop processors were awaiting policy guidance from the Trump administration on the size and scope of tax credits for U.S. biofuels producers that could bolster oilseed crushing and biodiesel margins, Luciano said.

An ethanol pioneer and for years the top U.S. producer, ADM's massive corn- and soybean-processing facilities supply biofuels makers including Marathon.

(Reporting by Karl Plume in Chicago; Editing by Rod Nickel)

((karl.plume@thomsonreuters.com; +1 313 484 5285; Reuters Messaging: karl.plume.thomsonreuters.com@reuters.net))