The Greeting Cards Association warned that thousands of jobs were threatened because the US wants to slap a 100 per cent import duty on the cards as a weapon in the dispute over banana import duties.
Ray Cousins, chairman of the association, said: "We are merely a pawn in a much bigger game. Greetings cards has been picked at random - it could have been anyone. People are very concerned because it is now clear this could become bogged down in bureaucracy and go on for months."
The US is also targeting the duty on other European Union imports worth half a billion euros (pounds 700m). Industries affected include cashmere sweaters, batteries, plastics, biscuits, bath oils, candles, lithographs, bed linen, cartons, wallets, handbags and cheese. Under US proposals, sanctions would start on 3 March.
UK industries would be hardest hit. In the cashmere industry, 700 jobs may be at risk in the Scottish borders. The DTI estimates 2,700 British jobs could be at risk.
The banana war blew up because the US was dissatisfied with a new EU regime for banana imports, introduced on 1 January. The regime was created to answer World Trade Organisation concerns that it protected imports from ex-colonies at the expense of US banana exporters such as Chiquita. The US claims that the regime is still too restrictive.
Yesterday, the WTO's Disputes Settlements Body in Geneva decided to reconvene its "bananas panel" to rule on the EU's banana regime, a move the US had tried to block.
"We believe the sanctions are illegal because there has been no ruling about them in international law," said a spokesman for Sir Leon Brittan, EU trade commissioner.
Brian Wilson, trade minister at the DTI, said: "It is quite wrong for one member of the WTO to decide unilaterally that another member has not complied. This dispute needs to be resolved in the framework of the WTO."
Ironically, the two biggest players in UK greetings cards, Hallmark and Carlton, are US-owned.