July 14 (Reuters) - Australia's Woodside Petroleum Ltd on Tuesday forecast a first-half loss of $4.37 billion after tax, as it joined oil majors BP and Shell in writing down several assets after a coronavirus-induced slump in oil prices.

The company said it expects to book non-cash, post-tax impairment losses of $3.92 billion related to the write down, and a further $447 million charge related to an onerous liquefied natural gas sale and purchase agreement. (Reporting by Shashwat Awasthi in Bengaluru; editing by Christian Schmollinger)