European Union experts are meeting to decide whether to impose an immediate ban on all livestock exports from the UK.
The EU Standing Veterinary Committee has gathered in the wake of the first foot and mouth outbreak in the UK for 20 years.
The disease has been confirmed at two sites - an abattoir in Little Warley, Essex, and a farm which sent 27 pigs there for slaughter.
A spokesman for the Ministry of Agriculture, Fisheries and Food says it expects to discover later today what action the EU committee will recommend. He said it is too early to say whether an export ban would be imposed.
The last outbreak of foot-and-mouth in the UK terrorised farming communities for months and led to the destruction of 500,000 animals.
British National Farmers' Union Ben Gill said: "This outbreak has potentially catastrophic implications for the whole of the British livestock industry. British farmers have had more than enough to deal with in the last few years without this latest blow."
Britain's chief veterinary officer Jim Scudamore delivered the stark warning after acknowledging that countries which import animals from the UK would be likely to expect strong measures to be taken in the wake of the outbreak at an Essex abattoir.
Mr Scudamore delivered the message as officials were set to begin the slaughter of more than 300 animals at Cheale Meats, in Little Warley, where the disease was discovered on Monday. He said: "It (a ban on live exports) is a strong possibility.
Mr Scudamore says a five-mile animal exclusion zone would remain around the abattoir, while MAFF has confirmed the disease had now spread to animals at Old England Farm which is adjacent to the abattoir and owned by the same family.
A five-mile animal no-go area has also been placed on two farms which delivered the first 27 pigs found to be infected to the abattoir last Friday. Officials have been unable to confirm the presence of foot-and-mouth at either of the farms - one in Great Horwood, Buckinghamshire, the other at Freshwater Bay on the Isle of Wight.
Junior agricultural minister Baroness Hayman would be making a parliamentary statement about the foot-and-mouth outbreak in the House of Lords this afternoon.
The ministry says it will hold a press briefing at its headquarters in London at 3pm.