* Liberals leave open possibility of forcing election

* Government announces C$500 million for job retraining

* Liberals say plan is just a rehash

* Opposition parties not definitive on plans (New throughout with Liberal leader's comments)

By Randall Palmer

OTTAWA, May 25 (Reuters) - Canada's official opposition Liberal Party said on Monday it may try to topple the minority Conservative government in Parliament in the next month if it does not make it easier to collect jobless benefits.

Liberal leader Michael Ignatieff dismissed as a "reannouncement" a C$500 million ($442 million) expansion of unemployment benefits unveiled by the government on Monday.

He will have an opportunity to move a motion expressing non-confidence in the government before Parliament adjourns for the summer on June 23, and told reporters that was a possibility.

"I can foresee it and I can foresee it in the near future, but I repeat the word 'foresee'," he said.