* S&P outlook cut on U.S. debt was expected - Rhee
* No evidence of serious spillover from Japan to rest of Asia
* Hard to see China accelerating yuan reform
By Rie Ishiguro
TOKYO, April 19 (Reuters) - The Asian Development Bank may need to slightly downgrade its forecast of 1.5 percent economic growth for Japan this year but a contraction in the economy is unlikely, Changyong Rhee, its chief economist, said on Tuesday.
"We have no reason to assume that the growth rate will be minus ... Supply chain elements we believe are less severe than we originally thought. On the other hand, the power shortage seems to have become a more serious problem," Rhee told Reuters in interview.
"We may have to adjust our number a little bit but it won't likely be a minus number."
The ADB's growth forecast for Japan in its Asian Development Outlook, compiled a week after the devastating March 11 earthquake and tsunami, is more bullish than most private sector analysts, some of whom predict a contraction for this year.
Rhee nevertheless played down expectations that rebuilding efforts will eventually bolster the Japanese economy, saying reconstruction would amount to only 4 to 5 percent of gross domestic product (GDP) at most and would pale in comparison to the extent of damage already done.
Asked about possible spillover to the rest of Asia, Rhee, a South Korean national, said he saw little sign that Japan's earthquake, tsunami and nuclear crisis would have a serious negative impact on Asian economies.
But he added that individual companies may already be hit by a shortage of goods imported from Japan.
"Many final goods manufacturing companies in South Korea heavily depend on parts and intermediate goods from Japan ... They are worrying about the possibility that this supply chain disruption may continue more than expected."
Asked about Standard and Poor's cut in its rating outlook for U.S. sovereign debt on Monday, Rhee said the action was expected and not a shock to Asian holders of U.S. Treasury bonds.
On currency issues, Rhee, a former G20 sherpa for South Korea, said it was hard to predict whether Chinese currency reform would gain traction as a result of Group of 20 discussions on including the yuan in the basket of currencies that make up IMF Special Drawing Rights.
He cited uncertainty about whether China would accept the preconditions for SDRs, such as liberalising its capital markets.
Rhee said the Group of Seven joint intervention last month to halt the yen's rise was well justified due to over-reacting markets but was "not a good message" for its G20 counterparts.
"It would have been much better if the G20, rather than G7, intervened. Now we are talking about exchange rate issues within G20 and many advanced countries talk about non-cooperation from emerging nations ... This could have been a good chance to build confidence in each other." (Editing by Edmund Klamann)