* Investors reverse previous session's trades
* Global stocks rise, yen slips, oil rebounds
* Wall Street set for gains
* Japan sees weaker economy
By Jeremy Gaunt, European Investment Correspondent
LONDON, April 13 (Reuters) - World stocks rose on Wednesday after recent declines, and Wall Street looked set to open higher with better-than-expected earnings from JPMorgan as a backdrop.
European stocks gained more than 1 percent.
Oil prices firmed as investors sought fresh opportunities to bet on riskier assets.
The Japanese yen fell after a brief show of strength in the previous session. The government downgraded its assessment of the economy for the first time in six months to reflect last month's devastating earthquake and tsunami and their aftermath.
Brent crude oil was above $121, halting a two-day decline, on fears that the Libya conflict could settle into a bloody stalemate, while a sudden disruption in Kuwaiti oil exports due to bad weather boosted sentiment.
Overall, Wednesday was mostly a mirror image of Tuesday, reflecting investors' current tendency to be risk-on one day and risk-off the next.
Surveys suggest that investors are willing to take riskier bets at the moment but are being constrained by concerns that growth in the global economy and, possibly, corporate earnings are vulnerable.
"The overriding theme at the moment is that the data we're seeing simply isn't conducive to building much confidence in the market," said Cameron Peacock, analyst at IG Markets.
World stocks as measured by MSCI <.MIWD00000PUS> were up half a percent for a 4.5 percent year-to-date gain. Much of the drive came from emerging markets <.MSCIEF>, which gained more than two-thirds of a percent.
Emerging markets have returned to favour in the past few weeks after a hiatus.
Japan's Nikkei <.N225> rose 0.9 percent on the day in thin volume. Analysts suggested the full impact of the country's disasters, as outlined in the government's new assessment, was still not clear.
A Bank of America-Merrill Lynch fund manager poll on Tuesday showed investors rapidly cutting their exposure to Japanese equities, although some big firms have been buying.
In Europe, the FTSEurofirst 300 <.FTEU3> rose 1.02 percent, rebounding from its biggest one-day fall in a month on Tuesday.
YEN WEAKER The yen slipped broadly while the euro hit a new 15-month high against the dollar at $1.4521 on EBS trading platform.
The prospect of further interest rate rises by the European Central Bank while monetary policy stays loose in the U.S. and Japan continued to buoy the single currency.
The dollar
"If there is no pullback in oil and other commodity prices then I think going forward the yen will be very vulnerable," said Niels Christensen, currency strategist at Nordea in Copenhagen.
On European bond markets, Bund futures handed back some of the gains from a rally in the previous session. (Additional reporting by Jessica Mortimer and Atul Prakash; editing by Stephen Nisbet)