Vietnam plans to appeal against a US decision to hit shrimp imports with an anti-dumping tariff of up to 93%.
Shrimp prices and industry jobs are under pressure
The US Commerce Department said that the move is needed because producers in Vietnam and China are selling shrimp at less than market prices.
Shrimp imports from China will now face duties of up to 112%.
The Vietnam Association of Seafood Exporters and Producers (VASEP) said that decision was "unjust" and that it would fight "until the end".
The organisation added that the tariffs "will have an adverse impact on the livelihood of millions of shrimp farmers in the coastal areas and thousands of workers in the shrimp processing factories in Vietnam".
China has yet to comment on the ruling.
Vietnam will be particularly hit by the tariffs, as shrimp is the nation's third biggest export item and the industry employs two million people.
VASEP said that almost two thirds of Vietnam's shrimp exports will be affected by the US tariff increase.
Both Vietnam and China have said their shrimp industries are simply more efficient than rival producers in the US.
The US shrimp organisation Southern Shrimp Alliance sees things differently.
It filed an anti-dumping petition last December, claiming that cheap imports had cut the value of the US shrimp harvest to $550m in 2002 from $1.25bn in 2000.
The trade body had requested tariffs of up to 200%.
Southern Shrimp Alliance President Eddie Gordon praised the decisions as "a critical step on the road to recovery for tens of thousands of fishermen, farmers and processors devastated by the massive volume of dumped Chinese and Vietnamese shrimp."
The US industry "is fighting for survival and on the brink of extinction from the tidal wave of dumped foreign shrimp", Mr Gordon said.
More to come?
Asian seafood farmers, meanwhile, accuse the US of blatant protectionism.
Last year Vietnam lost a bitterly fought campaign against a similar tariffs move by US catfish producers.
Officials at the Commerce Department have yet to give their judgement on four other countries named in the initial Southern Shrimp Alliance complaint - Thailand, India, Brazil and Ecuador.
For these the Commerce Department has said it will make a preliminary ruling by the end of July.
Analysts say the duties against China and Vietnam are likely to be enforced because the two countries are classified as "non-market economy" by the US.
By contrast they say it is much less certain whether the other four countries will be found against, as the US officially sees them as market economies.