SYDNEY: The Australian and New Zealand dollars fell against the greenback on Tuesday, as caution reined in markets ahead of the Federal Reserve's monetary policy meeting on Wednesday.

The Australian dollar was last down 0.21% at $0.7784, partially offsetting gains of half a cent in the previous day's session, which were underpinned by near-record high iron ore prices.

The currency faces resistance at $0.7816 it reached last week, but analysts believe it would likely continue to benefit from strong commodity prices in the near future.

"The close above 0.7790 is an important one and, if sustained, suggests that this move can extend towards the February highs at 0.80," Westpac Banking Corp strategists said.

The New Zealand dollar fell 0.17% to $0.7224 after gaining almost half a cent on Tuesday to $0.7236, its highest level since March 18.

The Kiwi dollar has been a beneficiary of strong commodity prices and weakness in the US dollar, which on Tuesday was hemmed into a narrow range as traders avoided taking big positions before the bond auction and Fed meeting.

US intermediate-dated Treasury yields rose on Monday after the Treasury Department sold $121 billion in debt to mixed demand, but benchmark 10-year yields were only 1 basis point higher at 1.570%.

Australian government yields on 10-year bonds matched that, adding 1 basis point to 1.69% on Tuesday.

New Zealand government bonds fell slightly, sending yields about 1 basis points higher across the curve. Ten-year bond yields were 4 basis points higher at 1.62%.