* Nikkei on course to lose 12 pct in 2018
* Topix likely to end year down nearly 18 pct
* Energy-related shares fall on overnight drop in oil prices
* Tokyo financial markets to reopen Jan. 4 after new year's break
By Daniel Leussink
TOKYO, Dec 28 (Reuters) - Japan's Nikkei struggled on its final trading day of the year on Friday as energy-related shares sagged, putting the index on track for its first annual loss in seven years.
The Nikkei share average fell 0.73 percent to 19,928.64 late in the morning session.
That put the benchmark index on course for a 12 percent decline in 2018, its first annual loss since 2011 and breaking the longest winning streak since the late 1980s.
The broader Topix lost 0.74 percent to 1,490.84, and was on track to lose nearly 18 percent this year.
Wall Street's three main indices staged a strong comeback on Thursday, surging from significant losses to end the session overnight in positive territory.
"U.S. equities were very volatile yesterday. It was a relief they ended positively after all, but because of the volatility it's hard to take risk on the Tokyo market," said Eiji Kinouchi, chief technical analyst at Daiwa Securities.
"Next week, Tokyo will only be open on Friday while New York will only close for New Years Day. The Tokyo market will be soft today as investors will take the volatility and holidays into account," he said.
Energy-related shares weighed on the broader market on Friday after oil prices sold off steeply overnight on worries about oversupply and an increasingly muddled outlook for global growth.
Petroleum product major Inpex Corp fell 1.2 percent, oil refiner Idemitsu Kosan shed 5.1 percent and Showa Shell Sekiyu KK lost 4.1 percent.
Shares of many index heavyweights dipped, with Toyota down half a percent, Sony Corp falling 1.5 percent and Nintendo off 1.0 percent.
Uniqlo-operator Fast Retailing and SoftBank Group gave up 1.6 percent and 1.1 percent, respectively.
Twelve out of the Tokyo Stock Exchange's 33 subsectors were in positive territory, led by sea transport and nonferrous metals.
Reporting by Daniel Leussink; editing by Richard Pullin