OTTAWA - Stephane Dion says the Liberals will back term limits of 12 to 15 years for senators, bringing the first modest step toward reforming Canada's Senate closer to reality.

The newly minted Liberal leader's decision breaks an impasse in the Senate, where the Liberal majority has been dragging its feet for months on Prime Minister Stephen Harper's bill to limit senators to eight-year terms.

However, Dion told The Canadian Press that his party won't budge in its opposition to a separate bill proposing the election of senators.

After meeting Tuesday with Liberal senators, Dion said they've agreed to support Harper's term limit proposal in principle. A second reading vote on the bill could now come by the end of next week.

However, Liberals will then propose amendments, to increase the term to at least 12 years and to ensure that no senator may be reappointed for a second term.

"Term limit is a good idea if it's not too short,'' Dion said in an interview.

He said the eight-year term proposed by Harper is too short and would potentially give the prime minister "exorbitant power'' to appoint every single senator in the chamber.

"That means that if all senators have a life expectancy as senators of eight years, a prime minister who would be there (in power) eight years would choose all the senators. He would renew completely the Senate after two mandates.''

Dion said a term of 12 to 15 years would be preferable. A prime minister couldn't appoint all senators without winning at least three mandates. Moreover, he said such a term would be long enough to produce experienced senators but short enough to encourage the appointment of younger senators.

At the moment, prime ministers tend to avoid appointing young senators because they can sit in the chamber until age 75.

When Harper appeared before a Senate committee to defend the term limit bill, he said he was open to amendments to lengthen the term and make it non-renewable. But even if the Tories now choose to oppose Dion's proposals, the Liberals hold the majority in the Senate and can force them through.

Once passed by the Senate, the bill would still have to win approval in the House of Commons, a reversal of the usual procedure.  The term limit bill was introduced in the Senate first since it directly involved changes to that institution.

Another Conservative initiative to begin holding Senate elections will get a much rougher ride.

Dion reiterated Liberal opposition to the idea of electing senators without simultaneously opening the Constitution to reform other aspects of the upper chamber, particularly the under-representation of western provinces.