* Trump rally may have been losing momentum - traders
* Steel sector weak after Moody's expresses negative views
By Ayai Tomisawa
TOKYO, Nov 30 (Reuters) - Japanese stocks edged up on Wednesday morning on the back of Wall Street's strength, but gains were limited as most investors stayed on the sidelines ahead of an OPEC meeting to decide on production cuts and a crucial referendum in Italy.
The Nikkei share average tacked on 0.2 percent to 18,345.95 in midmorning trade.
The benchmark index has risen 13 percent after Donald Trump's upset election win earlier this month, underpinned by expectations that the incoming administration would boost economic growth through increased infrastructure spending, corporate tax cuts and reduced regulation.
But traders said the post-U.S. election rally may be losing momentum.
"The expectations phase will likely end soon as investors are focused on what the real impact of the Trump administration would be on the market," said Yoshinori Shigemi, a global market strategist at JPMorgan Asset Management.
On the day, Shigemi expects subdued activity as traders looked to developments at the Organization of the Petroleum Exporting Countries (OPEC) meeting in Vienna later in the day.
He also said that investors were cautious as they waited for the U.S. jobs data on Friday and a referendum in Italy on constitutional change on Sunday, which could unseat the government of Prime Minister Matteo Renzi and stoke a nascent banking crisis.
Exporters were mixed, with Honda Motor Co rising 2.1 percent, Nissan Motor Co falling 0.4 percent and Panasonic Corp gaining 2.5 percent.
The dollar was steady at 112.430 yen. It had surged to 113.340 overnight on robust revised U.S. GDP data that showed the U.S. economy grew more quickly than initially thought in the third quarter for its best performance in two years.
Brokers were solidly bid, with Nomura Holdings gaining 1.0 percent and Daiwa Securities advancing 1.5 percent.
However, iron and steel stocks languished on outlook worries, with Nippon Steel & Sumitomo Metal Corp dropping 3.0 percent and JFE Holdings shedding 3.1 percent.
Moody's Investors Service said that the outlook for Asian steelmakers is negative in 2017 because demand from China will contract. It also said that trade frictions will curb steel exports and production in Japan, Korea and Taiwan, which export around 40-50 percent of their steel output.
The broader Topix rose 0.2 percent to 1,471.41 and the JPX-Nikkei Index 400 added 0.2 percent to 13,204.36.
(Editing by Shri Navaratnam)