* Euro tests 4-year peaks against yen, one-month top on US dollar

* Shanghai shares up, investors shrug off tensions over air zone

* Other Asian stock markets mixed, Japan ends lower

* European stocks seen opening flat to modestly higher

By Wayne Cole

SYDNEY, Nov 27 (Reuters) - The euro raced to fresh highs on both the yen and U.S. dollar on Wednesday, while Shanghai stocks shrugged off geopolitical concerns to outpace an otherwise lacklustre regional performance.

European stocks were poised for a subdued start with financial spreadbetters expecting flat to small gains for Britain's FTSE 100, Germany's DAX and France's CAC 40.

The single currency touched a four-year peak against the yen and a one-month high on the dollar as speculators wrestled with major chart resistance at 138.00 yen and $1.3600. A break here would likely open the way to further gains for euro bulls.

While most share markets were subdued after a flat finish on Wall Street, China's CSI300 of leading Shanghai and Shenzhen A-shares stood out with a 0.9 percent gain.

Investors there seemed unperturbed by the step up in tensions over Beijing's demands that airlines inform them when flying over disputed islands in the East China Sea, a move the White House termed "unnecessarily inflammatory."

The United States responded on Tuesday by flying two unarmed B-52 bombers over the region, while ANA and Japan Airlines stopped sending Chinese authorities their flight plans for routes that pass through the zone.

"It is bubbling away under the surface. In an environment where there's not a lot of data, then keeping one eye on geopolitics is probably going to be a good idea as well, because you never know what might come of that," said Sue Trinh, senior currency strategist at RBC Capital Markets in Hong Kong.

In truth there was no clear theme running through markets, except perhaps for a reluctance to get involved ahead of the U.S. Thanksgiving holiday on Thursday and next week's payrolls report.

Japan's Nikkei eased 0.4 percent to inch further away from the six-month peak touched on Monday. Conviction was equally lacking elsewhere, with MSCI's broadest index of Asia-Pacific shares outside Japan up 0.1 percent.

Wall Street had faded late on Tuesday after upbeat U.S. data on home building and house prices were offset by a disappointing reading on consumer confidence.

The Dow shed its early gains to end flat, while the S&P 500 Index eked out a 0.01 percent rise.

The Nasdaq managed to outperform thanks to gains in big-cap technology stocks and finished above 4,000 for the first time since the dot-com bubble burst in 2000.