A DROP in grain and meat exports has helped push Australia's trade balance further into the red.

The latest Australian Bureau of Statistics figures show the nation's overseas trade in goods and services was $1.85 billion in deficit in September, after allowing for seasonal factors.

It was the largest monthly deficit for 18 months, with an increase in exports more than offset by rising imports.

Exports were up by 5 per cent, with a 4 per cent slump in rural exports the only negative contribution.

The main "offenders'' were exports of cereal grains and cereal preparations (down by 10 per cent or $50 million), and meat and meat preparations (down by 9 per cent or $44 million).

On the import side, there were big rises in fuel and lubricants (up by 25 per cent or $448 million) parts for transport equipment (up by 25 per cent or $153 million).