Private messaging app Telegram is considering the biggest Pre-ICO in history to fund its new Blockchain platform and cryptocurrency.

As TechCrunch reports today citing ‘multiple sources,’ Telegram is aiming to raise up to $500 mln in private sales.

Its forthcoming Telegram Open Network (TON) would use the tokens for internal user payments.

Cointelegraph originally reported on TON in December, the scale of the endeavor only now becoming apparent.

According to sources, a series of private presales alone would raise “as much as $500 mln,” while the subsequent public distribution phase is planned to drive the value of the token to between $3 to $5 bln. This would make Telegram’s ICO easily the largest ever to have launched, dwarfing Block.One’s $700 mln offering last month.

Investors “beyond the inner circle” of CEO Pavel Durov may face a minimum $20 mln buy-in, TechCrunch continues, while others may be restricted to purchasing TON tokens with fiat, rather than Bitcoin or Ethereum as with previous ICOs.

“Top-tier institutional investment firms have expressed interest, but Durov is said to be wary of accepting their cash,” the publication reports as Russia continues its uncertain regulatory treatment of public digital token sales.

Telegram has faced controversy in recent months specifically in Russia after it refused to hand over user data to authorities in line with privacy laws.

A potential launch for the Telegram wallet has been set at Q4 this year, with the full package of services following in 2019.