Greece's Prime Minister Alexis Tsipras on Friday spelt out debt restructuring demands he wants international creditors to adopt, ahead of a weekend referendum he hopes will strengthen his position in negotiations.

In a television address, Tsipras called for "a 30 percent haircut off the Greek debt" and "a 20-year grace period" for the rest, to ensure "the viability of debt" in Greece, which currently stands at nearly 180 percent of its gross domestic product (GDP).