BRASILIA, Oct 1 (Reuters) - Brazil posted a $4.32 billion trade surplus in September, with exports totaling $24.28 billion and imports at $19.96 billion, the economy ministry said. The ministry revised down the trade surplus expected this year to $70.9 billion from $105.3 billion forecast in July. The revised forecast for total exports this year is $281 billion, down from $307.5 billion predicted in July, and total imports are now expected to be 210 billion, up from 202.2 billion forecast in July. Reporting by Anthony Boadle Our Standards: The Thomson Reuters Trust Principles.