Nov 28 (Reuters) - Australian shares are set to plunge at the open on Monday, extending losses from Friday, as investors are likely to exit riskier assets on the threat to economic recovery from the Omicron coronavirus variant cases detected in New South Wales. The local share price index futures fell 1.43%, a 113.3-point discount to the underlying S&P/ASX 200 index (.AXJO) close. The benchmark fell 1.73% on Friday. Across the Tasman Sea, New Zealand"s benchmark S&P/NZX 50 index (.NZ50) dropped 1.14% by 2129 GMT. Reporting by Harshita Swaminathan; Editing by Daniel Wallis