JAPAN last week announced it would allow US beef back into the country from February for the first time since 2003.
The premium market was worth $1.2 billion to the US in 2003 before the market was closed following an outbreak of bovine spongiform encephalopathy.
This comes as Australia last year sent 308,540 tonnes (shipped weight) of beef - the lowest volume since 2003.
US agriculture secretary Tom Vilsack confirmed on Monday import restrictions would ease from February 1, allowing US beef imports from cattle up to 30 months.
This will further ease a restriction in place since 2005 when Japan permitted US beef imports from cattle up to 20 months old after a total ban in 2003.
Now Australia's largest beef export market in volume and value terms, pre-BSE, Japan was the biggest market for US exports.
According to data provided by Meat and Livestock Australia, US research body Cattlefax forecasts that the alteration of the restriction would boost US beef exports to Japan by 25 per cent on last year's level of about 135,000 tonnes.
This would mean volumes of US beef imported into Japan this year would increase to about 168,000 tonnes.
MLA chief economist Tim McRae said it was bad news for Australian exporters.
"Basically, the easing restriction means instead of about 25 per cent of US beef being eligible to go to Japan, now about 90 per cent of US beef would be eligible," Mr McRae said.
But he said counteracting this was a forecast of tight supply due to the falling US beef herd - herd levels are at their lowest in 60 years - as well as strong prices from the US, in conjunction with the easing Japanese yen, which would affect Japan's ability to procure the beef.
"We always expected the change of age protocol would come."
Mr McRae said Australian grass-fed product shouldn't be too affected as it was cheaper and was underpinned by the fast food market, but the hit would be taken by the chilled, high-quality product, which has been declining in demand for the past few years.
Mr McRae said overall it would be "negative" for Australia.
According to the MLA projections released last week, Japan's share of Australia's global beef trade fell from 36 per cent in 2011, to 32 per cent last year, and is forecast to fall to 31 per cent this year.
The outlook for Australian trade to Japan this year looks tough, with volumes forecast to stay at about 310,000 tonnes.