Japanese shares fell 0.11 percent by the lunch break on Wednesday as investors focused on the knife-edge US presidential election.
The benchmark Nikkei 225 index at the Tokyo Stock Exchange gave up early gains to end the morning session down 9.98 points at 8,965.17, while the broader Topix of all first-section shares added 0.03 percent, or 0.23 points, to 745.11.
US President Barack Obama and his Republican challenger Mitt Romney were locked in a neck-and-neck duel for the White House, with exit polls from key swing states yet to confirm who will take the nation's top job.
"Regardless of who wins, some uncertainty will likely be removed," Kenichi Hirano, market analyst at Tachibana Securities, told Dow Jones Newswires.
"Investors can finally factor in specific policy implications from today on," he said.
The Tokyo market's initial gains tracked a rise on Wall Street with the Dow adding 1.02 percent, the S&P 500 up 0.79 percent and the Nasdaq Composite climbing 0.41 percent.
In Tokyo trade Wednesday, Nissan climbed 3.98 percent to 704 yen, despite the automaker slashing its full-year profit forecast by 20 percent on Tuesday as it pointed to a strong yen and slumping sales in China stemming from a bitter territorial row between Tokyo and Beijing.
On currency markets, the greenback bought 79.82 yen, down from 80.34 yen in New York on Tuesday, as US media reports pointed to an Obama victory in key battleground states -- a dollar-selling cue among traders.
The euro was at $1.2815, up from $1.2788 earlier Wednesday and marginally stronger than $1.2814 in US trade the previous day.