NEW YORK - Major League Soccer players have overwhelmingly voted to authorize the first strike in the league's history, which would wipe out openers scheduled to start March 25.

The league's first labour contract, a five-year deal, originally was set to run out Jan. 31 but was extended twice while negotiations continued. It expired Feb. 25 after the MLS Players Union refused another extension.

Unhappy with the single-entity structure that has seen the league negotiate all contracts since play began in 1996, players want greater free-agent rights and a higher percentage of guaranteed deals. The threat of labour strife comes as the Philadelphia Union, the league's 16th team, is set to start play. The Portland Timbers and Vancouver Whitecaps have been added for 2011.