Britain tried to contain an outbreak of highly infectious foot and mouth on Saturday, culling cattle at a farm outside London to prevent a repeat of the ruinous damage caused by the disease six years ago.
Prime Minister Gordon Brown broke off his holiday to return to London and chair an emergency meeting of senior ministers.
The European Commission said it had banned all live animal exports from the United Kingdom, as well as meat and dairy products from the infected area. Further restrictions could be brought in after EU veterinary experts meet on Wednesday.
The United States, which already has restrictions on imports of cattle and sheep from Britain due to other health scares, said it would also ban imports of pork and pork products.
Keen to avoid a repeat of the government's much-criticized response to the 2001 crisis, Brown said officials would work "day and night" to stem the outbreak identified on Friday.
Authorities set up a 3-km radius (1.7 mile) exclusion zone and a wider 10 km surveillance area around the infected farm in the county of Surrey. Within that area is a laboratory used by the Institute for Animal Health to test foot and mouth samples.
Movement of all pigs, sheep and cattle throughout the country was banned as a further precautionary measure.
Britain's chief veterinarian said the exact strain of foot and mouth was still being identified by scientists and said it was too early to say if the disease could be contained to one farm. She said reports of other foot and mouth infections were being investigated but would not say how many or where.
"It's only 24 hours into foot and mouth disease 2007 -- it is far too soon to say what the possible extent of the spread of this virus may be," Debby Reynolds told a news conference.
Despite the precautions, Ireland announced it was banning the import of British meat, livestock and non-pasteurized milk, and said it would not export live animals to Britain either.
Depending on how long the EU and U.S. bans remain in place, the impact on British agriculture could be profound. Industry experts said British exports of livestock and meat were worth around 15 million pounds ($30 million) a week.
In the 2001 outbreak more than six million animals were slaughtered, many of them burned on huge bonfires.
The cost to agriculture and rural tourism of that weeks-long outbreak was estimated at 8.5 billion pounds ($17 bln) and Brown's predecessor, Tony Blair, was strongly criticized for his government's handling of the problem.
On Saturday, workers from the agriculture department wearing protective suits, gloves and masks were seen herding the 60 or so infected cattle towards a pen where they were slaughtered.
The disease, which can travel on the wind and on farming equipment, causes high fevers and blisters in cloven-hoofed animals and often leads to death. It is very rarely transferred to humans and is not regarded as a public health threat.
Experts said Britain was better placed now to deal with the outbreak than it had been in 2001.
"We've got the administrative structures, we've got the infrastructure and we've got the scientific capability," leading microbiologist Hugh Pennington told the BBC. "Lessons have been learned and I'm confident we'll do much, much better this time."
With memories still fresh of the long-term damage caused by the outbreak six years ago, the farming industry backed the government's action.
"People have to understand that last time the delay occurred caused the further spread," National Farmers' Union president Peter Kendall said.
"Going through short-term inconvenience now is a price worth paying if we can keep this to a single location."