* Dollar hits 3-week high vs yen; stock gain, data weigh
* Euro gains limited ahead of ECB rate meeting on Thursday
* G20 looms, investors hope for agreement to spur economy (Updates prices; adds details, comments)
By Wanfeng Zhou
NEW YORK, March 31 (Reuters) - The dollar on Tuesday ended the first quarter on a high note, posting its best performance against the yen since December 2001, as a rally in stocks and weak economic data out of Japan dented the Japanese currency's safe-haven allure.
The yen fell to its lowest level in more than three weeks against the dollar after data showed Japanese unemployment hitting a three-year high and Prime Minister Taro Aso pledged to submit an extra budget to fund a new stimulus package to fight recession.
Wall Street gains helped to whet investor appetite for risk, boosting the euro and higher-yielding, commodity currencies like the Australian dollar.
"It seems yesterday's (stock market) sell-off was quite short-lived, and investors are once again loading up on riskier assets and currencies," said Robert Blake, senior currency strategist at State Street Global Markets in Boston.
The dollar rose as high as 99.36 yen <JPY=>, its highest since March, 5, according to Reuters data. It was last up 1.7 percent at 98.92 yen and advanced 9.2 percent this quarter.
Expectations that Japan's Tankan survey, due on Wednesday, will show a dramatic deterioration in business conditions, also weighed on the currency.
Analysts said the fundamental backdrop remains negative for the yen, with speculation that Japanese investors will likely start moving funds overseas again once the new fiscal year starts.
"Fiscal year-end had been holding people back from selling yen. But the fundamentals are absolutely horrendous, there's policy gridlock, and this lets Japanese investors continue to invest money abroad in droves," said Samarjit Shankar, global foreign exchange strategy director at The Bank of New York-Mellon in Boston.
The euro jumped 2.2 percent to 131.17 yen <EURJPY=>. Against the dollar, it rose 0.4 percent to $1.3258 <EUR=>, but was down about 5 percent in the first three months.
The Australian dollar rose 1.7 percent against the greenback to US$0.6949 <AUD=>.
G20, ECB IN FOCUS
Gains in the euro were limited as investors awaited Thursday's European Central Bank policy meeting. The ECB is expected to cut rates by half a percentage point to 1 percent and possibly signal plans for some form of unconventional policy such as buying bonds to boost the money supply.
"There's a lot of uncertainty about what the outcome of that might be and how it will affect the euro, maybe limiting flows into the euro today," State Street Global Markets' Blake said.
Analysts said the market was also beginning to focus on a summit of Group of 20 leaders of major industrialized and emerging economies in London on Thursday, with investors hoping for an agreement on measures to revive the global economy.
The G20 is expected to agree on increasing funding for the International Monetary Fund, but markets will also watch for any accord on global fiscal stimulus.
Any failure to reach agreement would cause a spike in risk aversion, analysts said, with the euro likely to suffer as attention turns to recent credit rating downgrades for Hungary and Ireland and a deepening recession in Eastern Europe.
One question the G20 summit is not likely to resolve is that of the dollar's future as global reserve currency. The issue has gained traction since China suggested wider use of the IMF's Special Drawing Rights currency basket.
But World Bank President Robert Zoellick said the dollar will remain the dominant reserve currency and a strong dollar is key to pulling the world out of crisis. For details, see [ID:nLV960479]. (Additional reporting by Steven C. Johnson; Editing by Jonathan Oatis)