* Chinese stocks tumble, with CSI300 index hitting 4-mth low
* Dollar scales more than 5-yr high vs yen
* Asian ex-Japan shares steady, Nikkei ekes out slim gain
* S&P cuts European Union debt rating to AA-plus from AAA
* Indonesian rupiah slumps to 5-yr low; baht, ringgit also down
By Dominic Lau
TOKYO, Dec 20 (Reuters) - Chinese stocks stumbled on Friday on concerns over a renewed cash crunch, while Asian shares crept higher as investors reassessed the Federal Reserve's policy outlook after it decided this week to start tapering stimulus.
The dollar climbed on the Fed tapering news to a more than five-year high against the yen, and stood tall against the euro and emerging currencies, while gold rebounded after earlier tumbling to a near six-month low.
China's benchmark money market rate climbed to a six-month high despite attempts by the People's Bank of China to calm sentiment, showing signs of a scramble for cash reminiscent of a massive crunch that occurred in June.
China's CSI300 stock index shed 2.2 percent after earlier hitting a four-month low, while shares of Hong Kong-listed Chinese companies sagged 1.7 percent.
"Liquidity is an issue," said Jackson Wong, Tanrich Securities vice-president for equity sales in Hong Kong.
"Even after the PBOC announced the short-term liquidity operation last night, there is still a concern in the short term because if the markets don't hear guidelines from PBOC officials, banks are still in the tight mode."
Financial bookmakers expected UK, Germany and French stocks to open up as much as 0.4 percent on Friday.
But their opening calls were made before ratings agency Standard & Poor's cut its supranational long-term rating on the European Union by one notch to AA-plus, citing rising tensions on budget negotiations and following cuts to the ratings of member states in recent months.
ASIAN SHARES TENTATIVE
MSCI's broadest index of Asia-Pacific shares outside Japan was little changed.
Tokyo's Nikkei benchmark erased earlier losses to end 0.1 percent higher, marking its highest closing level in six years for a second day in a row. The Bank of Japan, as widely expected, stood pat on its monetary policy after a two-day policy meeting.
Analysts said the Fed's smooth start in cutting its stimulus by $10 billion to $75 billion a month without disrupting markets removed one uncertainty for the BOJ, giving it more time to decide whether further monetary expansion will be needed next year.
The yen fell to its weakest level of 104.60 yen to the dollar since October 2008, while the euro eased 0.2 percent to $1.3637, hitting a two-week low.
Against a basket of major currencies, the dollar was up 0.1 percent at 80.735, a two-week high.
"With the Fed now having begun the tapering process, the burden of proof now seems to be on the side of the data to weaken sufficiently to force a halt," analysts at BNP Paribas wrote in a note.
Thursday's data showed U.S. home resales hit a near one-year low in November and new filings for unemployment benefits unexpectedly rose last week, dulling an otherwise brightening economic picture.
Overnight, U.S. stocks finished mostly flat as investors paused after a rally in the previous session, though the Dow Jones industrial average closed at its second record high in a row. U.S. S&P 500 E-mini futures inched up 0.1 percent in Asian trade on Friday.
Fears of renewed capital outflow put emerging currencies under pressure. The Indonesian rupiah slumped into a five-year trough of 12,250 per dollar on Friday, while the Thai baht touched a three-year low of 32.57 to the dollar and the Malaysian ringgit fell 0.3 percent to 3.285, a three-month low.
Among commodities, U.S. crude prices slipped 0.3 percent to $98.77 a barrel, paring some of Thursday's 1 percent rise on the back of U.S. refinery oil demand to meet robust distillate exports.
Gold rebounded 0.4 percent to $1,194.59 an ounce after earlier hitting a near six-month low of $1,185.30. The precious metal slumped 2.3 percent overnight, and is down nearly 29 percent this year, heading for its worst annual decline since 1981.