* China books unknown volume of U.S. soybeans
* Corn up on hopes for sales to China
* Wheat eases after gains on export hopes (Recasts throughout with U.S. market open, adds quote, updates prices; changes dateline, previous PARIS/SINGAPORE)
By Karl Plume
CHICAGO, Dec 18 (Reuters) - U.S. soybean futures rose for a second straight session on Tuesday as Chinese importers booked U.S. shipments in the second wave of purchases since striking a trade war truce with Washington earlier this month.
Corn also firmed as traders anticipated import purchases by China as part of the detente, which included a pledge by Beijing to buy U.S. agricultural products.
Wheat eased in a profit-taking setback after gaining about 1 percent a day earlier.
Chinese importers bought an unknown quantity of U.S. soybeans on Tuesday in the first major purchases since booking more than 1.5 million tonnes of U.S. soy shipments last week, three traders with knowledge of the deals said.
“This is positive news. If we keep doing this every week, it could really add up,” said Ted Seifried, chief market strategist for Chicago-based Zaner Ag Hedge.
The U.S. Department of Agriculture confirmed China’s soybean purchases last week, the first large deals in six months, and traders are anticipating further confirmation of sales as soon as Wednesday morning.
Chicago Board of Trade (CBOT) January soybeans were 3-3/4 cents higher at $9.08-1/4 a bushel at 12:20 p.m. CST (1820 GMT). CBOT March corn added 1-1/4 cents to $3.85-1/4 a bushel.
Both markets were also supported by concerns about adverse weather in South America. Heavy rains in parts of Argentina and southern Brazil and dry conditions in central Brazil have stoked worries that crop yields could be lower than initially expected.
U.S. President Donald Trump on Monday approved a second round of payments from an aid package of up to $12 billion to help farmers stung by the U.S. trade war with China.
CBOT March wheat fell 4 cents to $5.31-1/4 a bushel after gaining about 1 percent on Monday.
U.S. wheat has been bolstered by improving export data as well as signs that Russian wheat is becoming less competitive overseas.
Additional reporting by Gus Trompiz in Paris and Gavin Maguire in Singapore; editing by Ed Osmond and Dan Grebler