A MULTI-NATION trade deal, which could eventually add $2.6 billion a year to Australia’s agricultural exports, may be derailed by domestic US politics, federal Trade Minister Andrew Robb has conceded.

Mr Robb said the “anti-trade” stance of many US Democrats could prevent the finalisation of the 12-nation trans-Pacific Partnership.

US President Barack Obama is seeking approval from Congress to fast-track negotiations for the deal.

But Mr Robb said he feared the upcoming presidential primary vote could threaten the deal’s future.

Modelling from the US Department for Agriculture suggests Australia would benefit most of all 12 countries under the deal, with 19 per cent growth.

Mr Robb and the TPP have drawn criticism over the secrecy of negotiations and the inclusion of provisions allowing companies to sue foreign governments.