Tony Abbott has signalled his conviction that a referendum recognising indigenous Australians is more likely to succeed if it is "spiritually ambitious" but legally conservative.

Declaring that the timing and process for the referendum will crystallise within weeks, the Prime Minister said he was acutely aware of, and determined to avoid, the consequences of failure.

"There'd be nothing worse than having a go at this and finding that it fails because we've been too ambitious or, in the process of trying to do something wonderful, we've ended up dividing the country," Mr Abbott said in his most expansive comments on the referendum that is supported by both sides of politics.

He said the challenge would be to emulate the success of the 1967 referendum, which was carried with overwhelming support, but was "legally unambitious" while spiritually "very ambitious indeed".

"Sometimes the more legal ambition you've got, the less spiritual and ethical and cultural achievement you'll grasp and I think it's important to carefully weigh and consider these things in the weeks and months ahead," he said after his first discussions on the subject with indigenous leaders in north-east Arnhem Land.

Mr Abbott will discuss the referendum with indigenous leaders including Garrawuy Yunupingu, Noel Pearson and Warren Mundine on Wednesday, amid speculation that 2017 is the likely date for the question to  be put to the people.

Delaying the vote until then would, advocates say, maximise the prospects for building momentum, avoid the vote being politicised and draw of the euphoria of the vote 50 years earlier.

Asked by Fairfax Media if there was a danger that the question would fail to meet the expectations of those who say the question must be substantive, Mr Abbott replied: "We are really still at the beginning of this journey. We're not approaching the end.

"There is a lot of goodwill, there is a firm intention on the part of this government, on the part of the opposition, I think on the part of the Parliament generally, to embark on this journey, but it's got to be a successful one."

While there has been heated debate over whether the question should include a prohibition on racial discrimination, Mr Abbott said he was not going to rule specific proposals in or out.

"Generally speaking, the only proposals that I would rule out at this stage are proposals that would divide our country, and sometimes you only know whether a proposal would divide the country after it's been out there for a while and you've had a chance to gauge the reaction.

"My job here is not to be a private pontificator; my job is to be, as far as I humanly can, a national leader and national leaders do not rush into final decision making, given that the urgent task now is to bring forward a timetable and finesse a process.

"Once that's done, I think we're in a good position to start serious discussions over what the proposal might be."

 Mr Abbott suggested an announcement on timing and process was unlikely after Wednesday's talks, but added: "I do think we can crystallise this to the point of finalisation within a few weeks. I think it's important that everyone knows where our country is hoping to go.

"We shouldn't try to pre-empt the outcomes of this process, but there does need to be a clear process in place with an end point for our consideration."

An announcement on timing in the next few weeks would coincide with a parliamentary committee that includes Aboriginal MPs Ken Wyatt and Senator Nova Peris releasing its recommendation on the wording of the referendum question.

Follow us on Twitter