• Large 0.7130 option expiry anchors AUD/USD ahead of Fed event risk

• The size of the strike for the New York cut at 1400 GMT is A$1.3 billion

• Fed looks likely to raise its policy rate by 25 bps to 3.75-4.0% at 1800 GMT

• Ultra-hawkish Fed hike might depress AUD/USD through 0.7100

• 0.71085 was Monday's base; lowest level since August 20

• Next RBA rate decision on Sept 29: quarter-point hike to 4.6% looks likely

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(Robert Howard is a Reuters market analyst. The views expressed are his own)