By Praveen Menon, Lewis Jackson and Wayne Cole

SYDNEY (Reuters) -Australia on Saturday decisively rejected a proposal to recognise Indigenous people in the constitution, in a major setback to the country's efforts for reconciliation with its First Peoples.

Nationwide, with 45% of the vote counted, the "No" vote led "Yes" by 57.35% to 42.65%. Australian broadcaster ABC and other TV networks have projected that at least four states - New South Wales, Tasmania, Queensland and South Australia - would vote against altering the 122-year-old constitution.

A successful referendum requires at least four of the six states to vote in favour, along with a national majority. Because of Australia's time zones, voting in Western Australia was still under way as it became clear the referendum was lost.

Australians had to write "Yes" or "No" on a ballot paper that asked whether they agree to the proposal, which would recognise Aboriginal and Torres Strait Island people through the creation of an Indigenous advisory body, the 'Voice to Parliament'.

"I'm devastated," Indigenous leader and prominent "Yes" campaigner Thomas Mayo said on ABC News.

"We need a Voice. We need that structural change."

Australia's Indigenous citizens, who make up 3.8% of the country's 26 million population, have inhabited the land for about 60,000 years but are not mentioned in the constitution and are, by most socio-economic measures, the most disadvantaged people in the country.

Academics and human rights advocates fear a win for the "No" camp could set back reconciliation efforts by years.

The Voice to Parliament was proposed in the Uluru Statement from the Heart, a 2017 document crafted by Indigenous leaders that set out a roadmap for reconciliation with wider Australia.

Supporters of the proposal believe entrenching an Indigenous Voice into the constitution would unite Australia and usher in a new era with its Indigenous people.

Many Indigenous people favour the change, but some say it is a distraction from achieving practical and positive outcomes. The political opposition has criticised the measure, saying it is divisive, would be ineffective, and would slow government decision-making.

SETBACK FOR ALBANESE

Referendums are difficult to pass in Australia, with only eight of 44 succeeding since the country's founding in 1901. This is the first referendum in Australia in almost a quarter of a century. Australian voters rejected a 1999 proposal to become a republic.

In 1967, a referendum to count Indigenous people as part of the Australian population was a resounding success with bipartisan political support. The 2023 referendum has not garnered unified political support, with leaders of the major conservative parties campaigning for a "No" vote.

"The problem that the 'Yes' campaign had was they went and spoke to the leadership, the elites of this community, and they kept on saying: 'We've got these communities'," said Warren Mundine, a leader of the "No" campaign across the country.

The Voice has been a key feature of Prime Minister Anthony Albanese's term in office, and a referendum loss would stand out, political analysts say, as his biggest setback since coming to power in May last year.

"The task ahead for us is to come together and chart a new path forward," Foreign Minister Penny Wong said.

"I don't know yet what that would be but it's something that we can do as a country."

(Additional reporting by Kirsty Needham, Alasdair Pal and John Mair in Sydney; Writing by Praveen Menon; Editing by William Mallard, Clarence Fernandez and Edmund Klamann)