UPDATE: A BUSHFIRE in Victoria's southwest has the potential to impact properties and is unlikely to be brought under control soon.

Victoria's Fire Services Commissioner Craig Lapsley said significant work would be done on fighting the fire at Kentbruck, near Portland, but he is no longer confident the fire will be brought under control today.

The fire is slow moving, but has the potential to impact properties in the Mumbannar, Winnap, Drik Drik, Greenwald areas, the Country Fire Authority watch and act messages say.

The fire has crossed the Winnap-Nelson Rd and the Glenelg River and is travelling in a north-westerly direction towards Mumbannar and Winnap.

Mr Lapsley told the ABC authorities hoped to have the fire in the best position possible ahead of further hot weather on Tuesday, but he was not confident it would be contained today.

He said the fire was in farming area and there were no communities under direct threat.

Roads and campsites in the area are closed.

Two South Australian Country Fire Service strike teams have been deployed across the border to help contain the bushfire, which has been burning since Friday.

CFS regional duty officer Scott Murray said the team, of about 50 CFS firefighters and forward personnel, would return to SA on Monday night with similar numbers to be deployed across the border on Tuesday and Wednesday.

Smoke from the Victorian fire has drifted across eastern parts of South Australia in recent days, affecting regional centres including Mt Gambier.