* Budget to be unveiled May 2
* Minister trims 2013 growth outlook to 1.5 pct from 2.2 pct
* Gov't needs the support of another party to avoid election
TORONTO, April 22 (Reuters) - Ontario's budget deficit was C$9.8 billion ($9.54 billion) in 2012-13, down from the minority Liberal government's January forecast of C$11.9 billion, provincial Finance Minister Charles Sousa said on Monday.
In the text of a speech to be delivered at a business lunch in Toronto, Sousa said the government will deliver its 2013-14 budget on May 2.
The smaller-than-expected deficit could help ease the way for the Liberals, under new Premier Kathleen Wynne, to win the support of the left-leaning New Democratic Party in the provincial legislature and avoid a snap election.
Sousa said the government expects Ontario's economy to grow 1.5 percent in 2013, down from its previous 2.2 percent forecast, and he maintained the government's target of balancing the budget by 2017-18.
The Liberals' C$11.9 billion deficit forecast in January was itself a sharp reduction from the C$14.4 billion the government projected last fall.
Sousa was named finance minister in February after Wynne replaced Dalton McGuinty as premier.
The centrist Liberals need support from at least one of the opposition parties, either the NDP or the right-wing Conservatives, to pass the government's budget in the Legislature and avoid an election.
Conservative leader Tim Hudak has already said his party will vote against the budget.