Rudd says he wants to let the public know his change of mind before any vote on an Australian Greens private members bill on gay marriage that will be first debated in the federation chamber, an offshoot of the lower house, next Monday.
Foreign Minister Bob Carr says the numbers may be shifting in support of legalising same-sex marriage among parliamentarians.
The Lower House selection of bills committee is yet to lock in a date for a vote, but June 6 is being considered.
Greens MP Adam Bandt warned the public "won't treat kindly" any delay tactics designed to avoid Prime Minister Julia Gillard having to join Opposition Leader Tony Abbott in voting against the bill.
Gillard challenged Abbott to "follow in the footsteps" of John Key and British Prime Minister David Cameron and allow his MPs to have a conscience vote on gay marriage.
Abbott reiterated the Coalition's position of support for the status quo.
Liberal frontbencher George Brandis said Rudd's comments were more about personal ambitions than about the issue of same-sex marriage. "What it tells you is that Kevin Rudd has not given up. Kevin Rudd is at it again," he told Sky News.
Meanwhile, moves to legalise gay marriage cleared a crucial parliamentary hurdle in Britain as it emerged that civil partnerships could be abolished as the price for getting Cameron's plans on to the statute book.
A wrecking amendment tabled by Conservative opponents of same-sex marriage was defeated by 375 to 70 votes after the Tory front bench was supported by the vast majority of Labour and Liberal Democrats.
As the Commons debated the Marriage (Same Sex Couples) Bill, Labour threw Cameron a lifeline in his latest battle with Tory right-wingers.
He faced the prospect of losing the vote on the wrecking amendment, which could have delayed the introduction of gay marriage until after the election.
A threatened Conservative rebellion faded with fewer than 50 backbench MPs voting against the leadership line. The outcome - five days after 116 of his MPs defied Cameron in a Commons vote on Europe - will be a relief to the Prime Minister.
Ahead of the vote, the Government agreed to review the future of civil partnerships. The Tory rebels proposed extending civil partnerships to heterosexual couples.
Labour and the Liberal Democrats agreed to support the review as they joined forces with Cameron.
A senior Conservative source said the review would begin shortly, with a view to completing it by the 2015 general election and would look at all options, including scrapping the ceremonies, telling the Independent: "How civil partnerships work and whether they continue to exist, the whole thing would be up for grabs."
- Independent, AAP
