* Traders await details on U.S.-China trade deal
* Advances extend annual gains from 2019
* USDA set to release export sales data on Friday
CHICAGO, Jan 2 (Reuters) - U.S. grain and soybean futures rose on Thursday as fresh buying entered the markets to start the new year and traders continued to expect increased Chinese demand.
The most actively traded soybean futures reached their highest price since June 2018, while wheat futures set the highest price for a most-active contract since August 2018 at the Chicago Board of Trade.
Gains were fueled by hopes for major U.S. agricultural sales to China, the world's top soybean importer, following the Phase 1 trade agreement struck last month. U.S. President Donald Trump said on Tuesday the initial deal would be signed on Jan. 15. It includes a commitment by China to buy more American agricultural products, although details have not been announced.
China slashed imports of U.S. farm goods during the countries' trade war, hurting crop prices, after Beijing imposed steep retaliatory tariffs on American soybeans, grain sorghum and other products.
"If you don't see a consistent uptick in bushels moving, you're going to have a hard time sustaining a lot of excitement," said Matt Wiegand, broker for FuturesOne.
Most-active soybean futures were up 0.3% at $9.58-1/2 a bushel at 12:35 p.m. CST (1835 GMT). The most active CBOT wheat contract rose 0.4% to $5.61 a bushel, while corn edged up 0.8% to $3.91 a bushel.
The advances extended annual gains in the markets from 2019. But soybean and wheat futures could see setbacks soon after recent rallies, analysts said.
"You've got a little bit of money flow with the new year," Wiegand said.
The U.S. Department of Agriculture at 2 p.m. CST (2000 GMT) on Thursday is set to release a monthly oilseed crushings report. It is expected to show 5.277 million short tons, or 175.9 million bushels, of soybeans were processed in November, according to a Reuters survey of analysts.
The USDA on Friday is due to report weekly export sales of grains and soybeans, a day later than usual due to the New Year's Day holiday on Wednesday.
(Reporting by Tom Polansek in Chicago; Editing by Andrea Ricci)