The England midfielder hobbled past reporters following a training session which was due to be partially open to the media but ended up taking place entirely behind closed doors.
Asked if he would be able to play on Sunday, Beckham nodded in the affirmative while Galaxy coach Bruce Arena said: "David will be fine, David will be fine.
"David has trained for the past three days and there is nothing wrong with David," said Arena who declined to explain why the session was closed to the media.
Beckham, who picked up the injury in the playoff win over Houston, said on Friday he would take a pain-killing injection before Sunday's game.
THIRD TITLE
Victory in the final would bring Beckham his third league title in a third nation following his championships in England with Manchester United and Spain with Real Madrid.
The game is Major League Soccer's showcase event, a date they hope will eventually be considered the Super Bowl of soccer and Beckham is at the heart of the league's marketing plans.
But since the player arrived in Seattle on Thursday to begin preparing for the game on the artificial surface at Qwest Field, it has gradually become evident he is struggling for fitness.
As well as the ankle injury, Beckham looked under the weather during his news conference on Friday, coughing and sniffling.
His captain Landon Donovan, in paying tribute to Beckham's commitment to the team, also revealed his team mate had been below par for some time.
"This guy has been hurt or sick for probably the last six or seven games but he gets on with it and he plays. That's helped our team a lot," said Donovan.
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