CHICAGO (Reuters) - A second round of tariff-related aid to U.S. farmers could be announced in December, according to a white paper released by the U.S. Department of Agriculture on Thursday.

The government model used to account for growers' losses may factor in new tariff levels enacted against trade partners, such as China or the European Union, according to the paper. It does not state how much money could be directed to farmers, or how such funds would be split up.

The aid package, originally announced at $12 billion in July, includes cash payments for farmers of soybeans, sorghum, corn, wheat, cotton, dairy and hogs.

The USDA said in August that its farm aid package would - in the first part - include $4.7 billion in direct payments to farmers to help offset losses from retaliatory tariffs on U.S. exports this season.

It also includes $1.2 billion in government purchases of fruits, nuts, rice, legumes, beef, pork and milk for distribution to food banks and nutrition programs, as well as some $200 million for a trade promotion program to develop new markets.

"The second part will be announced, if necessary, in December and may account for other factors, such as new tariff levels, regional basis effects, or other market conditions that may have mitigated some of the trade damages," according to the paper.

(Reporting by Julie Ingwersen in Chicago; Additional reporting by Mark Weinraub in Chicago; Writing by P.J. Huffstutter in Chicago; Editing by Paul Simao)