OTTAWA - The federal government is poised to issue a firm policy direction on Old Age Security in the upcoming budget centred around raising the age when retirees can start to collect.

Several government sources tell The Canadian Press that the budget will lay out a path forward, rather than launch a national conversation or policy paper on proposed changes.

There's considerable discomfort within the Conservative caucus on OAS changes.

The leading option is to increase the age of eligibility to 67 from 65 -- an option Prime Minister Stephen Harper has publicly confirmed is under consideration.

The plan is to phase in the changes slowly and begin the process in a few years.

Sources say one top possibility -- as uttered vaguely by Finance Minister Jim Flaherty last week and then retracted -- is to start phasing in the increase in age in 2020, and fully implement the change over five years.

Under that scenario, anyone now aged 57 or older would not be affected.