SYDNEY (Reuters) - Australia's conservative government said on Monday it had postponed the release of a mid-year budget update due to a security alert in Sydney, where hostages are being held in a cafe in the central business district.

Treasurer Joe Hockey had been due to announce updated deficit and spending plans in his mid-year economic and financial review at 0130 GMT (9:30am Singapore time).

Prime Minister Tony Abbott was due to appear at a news conference to discuss the hostage crisis.