* New hearing between May 9 and 16
* Massmart shares down 2.5 percent in rising market
* Govt, unions concerned about jobs
(Recasts with government comments in par 6, updates shares)
By Tiisetso Motsoeneng
JOHANNESBURG, March 22 (Reuters) - South Africa's antitrust watchdog postponed hearings into Wal-Mart's $2.3 billion bid for a controlling stake in domestic retailer Massmart after the government and unions asked for more time to submit additional information.
Competition authorities are the last obstacle to the world's biggest retailer taking a 51 percent stake in Massmart after shareholders overwhelmingly voted in favour of the deal in January.
The deal has pitted Wal-Mart against South Africa's trade unions, some of which have threatened to strike against the U.S. giant.
The Competition Tribunal said on Tuesday it would "reluctantly" push back the hearing dates to between May 9 and May 16 to allow government departments and the union more time to make submissions.
The tribunal will hear arguments from Economic Development, Trade and Industry and the Agriculture, Forestry and Fisheries Departments and the South African Commercial, Catering and Allied Workers Union (SACCAWU) on the set dates.
Government and unions are concerned the deal could lead to job losses and to unfair conditions of trade being imposed on domestic suppliers due to Wal-Mart's purchasing power.
"Is that (deal) going to benefit us in terms of jobs or not? I think that is the issue," Trade and Industry Minister Rob Davies told lawmakers in Cape Town.
Meanwhile, a handful of SACCAWU members picketed outside the offices of the Competition Tribunal, demanding it block the deal or attach tough conditions.
"We believe it is not in the best interest of South Africa for Wal-Mart to be allowed into our country," SACCAWU General Secretary Bones Skulu said in a statement.
SACCAWU has formed an anti-Wal-Mart coalition with other labour and activist groups.
Shares in Massmart closed down 2.5 percent at 130.37 rand, lagging a 0.64 percent gain for the JSE Top-40 blue-chip index.
Wal-Mart shares were little changed, in line with the broader market on Wall Street. (Additional reporting by Gugulakhe Lourie and Wendell Roelf; Editing by Hans Peters and Will Waterman)