Alex Salmond's Cabinet is due to consider gay marriage on July 17. Civil partnerships have existed since 2005.
The Scottish Government consulted last year on whether gay couples should have the option of religious weddings. It is understood 77,000 responses were received, but 20,000 were postcards from groups outside Scotland. Most responders were hostile, but the balance shifted if postcards were excluded.
Ministers stress religious groups will not be forced to hold ceremonies, something which could require Westminster to amend equality law.