(Refiles to fix first bullet after BOJ decision)
* BOJ keeps ultra-loose monetary policy
* Subaru tumbles after co says it halted output at sole factory in Japan
* Bridgestone falls after it says to buy Tomtom's Telematics for $1 bln
* Dec exports fall more than expected
By Ayai Tomisawa
TOKYO, Jan 23 (Reuters) - Japan's Nikkei wavered on Wednesday as weaker-than-expected December exports and concerns over U.S.-China relations added to worries about the outlook for the trade-reliant economy, though a softer yen offset pressure on exporters.
The Nikkei share average was little changed at 20,631.54 points at the midday break, after flitting between negative and positive territory.
As expected, the Bank of Japan trimmed its inflation forecasts but maintained its ultra-loose monetary policy at the end of a two-day meeting on Wednesday.
But trade was the key worry of the day.
A report by the Financial Times that the United States had rejected China's offer for preparatory trade talks rekindled worries about their dispute, though White House economic adviser Larry Kudlow later denied it.
Prior to the market open, Japan reported exports in December fell the most in more than two years and by more than expected, dragged by plummeting shipments to China and regional markets as weak global demand and U.S.-Sino trade frictions take their toll on the economy.
"Japan is in a difficult position because of its economic reliance on the U.S. and China. Japan's cyclical stocks depend on demand from the two counties," said Takatoshi Itoshima, a strategist at Pictet Asset Management.
Some exporters trimmed their drops and gained as the dollar rose 0.3 percent to 109.64 yen, recovering from 109.4 yen in early Asian trade. Advantest Corp added 0.1 percent and Honda Motor Co added 0.1 percent.
Subaru Corp stumbled more than 5 percent after the automaker said its sole car factory in Japan had halted output a week ago after it discovered a defect in a component.
Bridgestone Corp plunged 3.7 percent after the tire maker said it will buy TomTom's its fleet business Telematics for $1 billion.
Japan Display Inc jumped 11 percent after the Wall Street Journal reported that the company is in investment talks with Taiwan's TPK Holdings and Chinese state-owned Silk Road Fund.
The broader Topix fell 0.2 percent to 1,553.86. Declining issues outweighed advancing ones 1,349 to 664. (Editing by Kim Coghill)