* Steadier commodity prices drive slight share gains
* Fed comments reassure investors
* Euro still weak against dollar as Greek woes persist
LONDON, March 23 (Reuters) - World stocks traded flat to marginally higher on Tuesday, supported by steadier commodity prices but the euro hovered near a three-week low versus the dollar, weighed down by uncertainty over Greece's debt crisis.
Early Asian and European trade saw gains triggered by a strong overnight close for Wall Street which had risen after the passing of landmark legislation to reform healthcare, with pharmaceutical stocks driving gains..
There was also a rebound on gold, which rose off the lowest levels in nearly a month, while U.S. light crude recovered slightly after sinking to three-week lows in the previous session.
The MSCI main world equity index was flat by 1245 GMT, though the FTSEurofirst 300 index of pan-European blue-chips was up 0.3 percent thanks to gains of over 10 percent from oil firm Cairn and higher-than-expected profits at British insurer Legal and General.
But worries about Greece ahead of a European Union summit are keeping a lid on gains for riskier assets as concern grows that EU leaders will be unable to agree a support package for the country.
"Markets are looking for news but with Greece bubbling away in the background and the uncertainty about China and the U.S. (on yuan revaluation) the best strategy seems to be to play ranges," said Nigel Rendell, a strategist at RBC in London.
Attention is now turning to U.S. existing homesales data due at 1400 GMT to gauge the situation on the housing market which remains one of the weakest segments of the U.S. economy.
Sales are expected to slip to 5 million in February from 5.05 million last month, according to Reuters data.
U.S. S&P stock futures were slightly higher and Nasdaq 100 futures added 2.25 points.
"A positive homesales number will add confidence that the economy is on the right track and that the recession has been contained," said Andre Bakhos, president of the Princeton Financial Group in North Brunswick, New Jersey.
Senior Fed officials' comments that the U.S. central bank remained committed to maintaining loose monetary conditions have also helped reassure investors startled by India's surprise move on Friday to hike its interest rates.
President of the Federal Reserve Bank of Atlanta Dennis Lockhart said the Fed's pledge to keep rates ultra-low for an extended period was appropriate.
His counterpart in Chicago said he strongly supported keeping the current loose monetary stance as long as inflation remained under control.
Emerging economies such as India are facing rising inflationary pressures, caused in part by an influx of capital, but consumer price rises in developed Western economies are broadly slower.
But British consumer prices rose at a slower rate than expected in February, sending sterling to its lowest in nearly two weeks. Emerging stocks rose 0.4 percent while emerging sovereign spreads tightened two basis points to trade at 262 bps over U.S. Treasuries.
The dollar rebounded 0.3 percent against a basket of major currencies, keeping the euro near its weakest level against the greenback in three weeks..
Ahead of a European Union summit on Thursday and Friday, members of the grouping remain divided on what to do about help for debt-stricken Greece.
Greece said it wants a European solution to its debt crisis but Germany, the economic powerhouse of the euro bloc, has resisted calls for an aid package. "It is looking increasingly unlikely there will be an EU aid package for Greece which leaves the euro in a negative position," said Ian Stannard, senior currency strategist at BNP Paribas in London.
U.S. Treasuries were little changed ahead of the housing data and a $44 billion auction of two-year notes.
(Reporting by Sebastian Tong and Sujata Rao; Editing by Ron Askew)