Indonesia's president has proposed to move the capital from Jakarta, a crowded and polluted city of 10 million people, to the island of Borneo.

Jakarta is one of the fastest-sinking cities on earth and environmental experts warn that one third of it could be submerged by 2050 if current rates continue.

Decades of uncontrolled and excessive depletion of groundwater reserves, rising sea-levels, and increasingly volatile weather patterns mean swathes of it have already started to disappear.

President Joko Widodo suggested a new capital in Kalimantan, on the Indonesian side of the island shared with Malaysia and Brunei, in a speech to parliament, a day before the country's independence day holiday.

However, he left Indonesians guessing as to the exact location.

"I hereby request your permission to move our national capital to Kalimantan," said Mr Widodo, who will be sworn in for a second term in October after winning an election in April.

"A capital city is not just a symbol of national identity, but also a representation of the progress of the nation. This is for the realisation of economic equality and justice," he added.

He did not give the exact site of the new city in a region known for rain forests, coal mines, orangutans and home to just over 16 million people.

The president toured Kalimantan in May to survey potential sites and last month tweeted a shortlist of three provinces: Central, East and South Kalimantan.

The new capital should tick several boxes, officials say.

"A capital city is not just a symbol of national identity, but also a representation of the progress of the nation."

It must be in the centre of Indonesia, an archipelago of more than 17,000 islands that stretches some 5,000km from its western to eastern tips.

The risk of natural disasters should also be lower than other parts of Indonesia often hit by earthquakes, floods and volcanoes.

Jakarta is one of the world's most densely populated cities, home to more than 10 million people and three times that number when counting those who live in surrounding towns.

The city is prone to floods and sinking due to subsidence, caused by millions of residents using up groundwater and leaving rock and sediment to pancake on top of each other.

Moving the capital to a safer, less congested location would cost up to $33 billion, according to planning minister Bambang Brodjonegoro.

The price tag includes new government offices and homes for about 1.5 million civil servants expected to pack up and start moving in 2024.

Indonesia is not the first Southeast Asian country to move its capital.

In 2005, Myanmar's ruling generals moved abruptly to Naypyidaw, a town in remote hills about 320km away from the colonial era capital, Yangon, and the occasional mass protests that erupted there.

In the 1990s, Malaysian leader Mahathir Mohamad built an administrative capital in Putrajaya, about 33km from Kuala Lumpur, one of the mega-projects that helped to define his first stint in power.

Mr Widodo had been expected to announce the location of Indonesia's new capital today, but authorities have been cautious about revealing too much, fearing the news would send land prices soaring.