* Portugal bond yield at new high as bailout fears grow
* Metal prices, Aussie fall after China rate rise
* Euro slips; world stocks end five-day winning streak
(Adds U.S. stock futures, China graphic)
By Dominic Lau
LONDON, April 5 (Reuters) - Portuguese bond yields rose to euro lifetime highs on Tuesday as the country moved closer to a possible debt bailout, hitting the euro, which fell further from a five-month peak versus the dollar after China raised rates.
Metal prices and the Australian dollar, seen as a proxy for Chinese growth because of raw materials exports to the world's second largest economy, fell after Beijing hiked interest rates for the fourth time since October to cool inflation.
China's tightening also dented Brent crude prices, which pulled back further from 32-month highs but stayed just above $120 a barrel as markets focused on fears that unrest in producer states in Africa and the Middle East could disrupt supply.
Global stocks snapped a five-day winning streak, and U.S. stock index futures fell 0.2 to 0.7 percent, indicating a weak start on Wall Street.
Rating agency Moody's earlier cut Portugal's sovereign debt by one notch, saying it believed the incoming government would urgently need to seek financial aid from the EU.
"Even though Moody's still rates the sovereign two notches higher than Standard & Poor's, the downgrade is another blow to sentiment," said Gavan Nolan, an analyst at data monitor Markit.
There were also reports that Portuguese banks may be threatening to stop buying government bonds to pressure Lisbon into seeking a bailout, following the same path as Greece and Ireland.
Yields on Portugal's 10-year government bonds rose to 9.033 percent, while Portuguese stocks fell 0.9 percent, underperforming the broader FTSEurofirst 300 index, which was flat.
Credit default swaps implied a 41 percent probability of a Portuguese default within five years, compared with 33 percent at the end of February, data provider CMA said.
EURO PRESSURED
The euro was down 0.4 percent at $1.4163, off a five-month high of $1.4268 hit on Monday, and down 0.1 percent at 119.39 yen, while the Australian dollar fell 0.5 percent to $1.0318.
Market doubts over whether the single currency can make fresh gains given that players have already positioned themselves for interest rate rises in the euro zone during 2011 also put pressure on the euro, which has risen 5.9 percent against the dollar and 9.9 percent versus the yen this year.
"There is a lot of good news priced into the euro already and (ECB President Jean-Claude) Trichet will have to support the rate view to keep the positive momentum," said Niels Christensen, currency strategist at Nordea in Copenhagen.
The European Central Bank is widely expected to raise rates by 25 basis points on Thursday from a record low of 1 percent to tame inflationary pressures.
OIL IMPACT
Federal Reserve Chairman Ben Bernanke said late on Monday that the recent spike in U.S. inflation was unlikely to persist.
But a sustained higher oil price could pose a serious threat to the global economic recovery and dampen risk appetite, and commodity price pressures saw silver rise to a 31-year high.
"The recent rally in oil has had virtually no impact on equities. It was just over a month ago where equities markets were nervous about the impact of oil prices on the economy," Deutsche Bank strategist Jim Reid said in a note.
"The difference this time is that the rise has likely been due to decent growth rather than immediate geopolitical concerns. Nevertheless one would expect the creeping price of oil to start to get more attention given the recent rally."
World stocks measured by MSCI All-Country World Index fell 0.3 percent after hitting six-week highs in the previous session, while emerging market shares were flat.
In Asia, Japan's Nikkei average lost 1.1 percent with investors still wary about the long-term impact of last month's massive earthquake and tsunami and a resulting nuclear accident that workers are still struggling to contain.
Brent crude eased after hitting a 32-month high of $121.29 on Monday as Nigerian election delays and a short-lived strike in Gabon added to supply jitters for a market already on edge over fighting in Libya and unrest in Yemen, which borders top producer Saudi Arabia.
Silver dipped 0.3 percent after rising to its highest since early 1980 at $38.77 an ounce before the Chinese rate rise, while gold fell 0.3 percent and copper lost 0.2 percent, down for the third day in a row.
(Additional reporting by Emelia Sithole and Jessica Mortimer in London, and Alex Richardson in Singapore; editing by Patrick Graham and John Stonestreet)