SYDNEY (Reuters) - Australia's ruling coalition, trailing in the opinion polls, brought forward its annual budget by two months, according to a parliamentary timetable published on Monday, signalling it will call an election at the latest possible time.

       Instead of the usual date of the second Tuesday in May, the conservative government of Prime Minister Scott Morrison plans to deliver the budget on March 29, the schedule showed.

       Since Australian national elections are typically called five weeks in advance and take place on Saturdays, the earliest likely polling date would be May 7, 2022.

       They must also take place at least every three years. The country's last election was in May 2019, meaning the government plans to run close to a full term.

       Morrison's personal approval rating is hovering near its lowest levels in 18 months following a slow COVID-19 vaccination program and prolonged lockdowns and border closures.

       Polls have also persistently shown his Liberal-National Party coalition trailing the opposition centre-left Labor party.

       (Reporting by Byron Kaye; editing by John Stonestreet)