(Updates with closing prices)

By Kevin Buckland

TOKYO, May 20 (Reuters) - Japan's Nikkei share average

ended flat on Tuesday, as support from a pause in the yen's

rally lifted automakers and exporters, while investor sentiment

remained cautious following U.S. sovereign downgrade by Moody's

last week.

At the same time, uncertainty ahead of a three-day Group of

Seven meetings of finance ministers and central bank chiefs in

Canada later in the day makes it "difficult for traders to

move," said Maki Sawada, a strategist at Nomura.

Finance ministers will strive for unity on non-tariff issues

at the gathering, but may have trouble reaching consensus with a

Trump administration intent on pushing allies to serve U.S.

interests.

The Nikkei index held its ground at 37,529.49, while

the broader Topix was also steady at 2,738.83.

Investors worry that U.S. officials may push for a weaker

dollar as part of tariff negotiations. Japan's top trade

negotiator said on Tuesday there was no change to Tokyo's stance

of demanding an elimination of U.S. tariffs in bilateral trade

negotiations.

Trade tensions with China are also far from resolved, in

spite of a recent rapprochement.

"This is not an environment where we can be complacent about

the Sino-U.S. trade relationship," said Nomura's Sawada.

"Developments are likely to continue to swing stock markets."

Car manufacturers and suppliers rose 0.7% as a

sector, while non-ferrous metals led gains with a

1.89% advance.

The yen strengthened to 144.31 per dollar on

Monday, extending a rally from 148.455 a week earlier, but has

since stabilized.

Strength in chip-related shares was another factor pulling

the Nikkei higher, with Advantest ( ADTTF ) gaining about 3%.