The suspension, which went into effect on April8, covers live birds, poultry and poultry products, said Singapore's Agri-Food and Veterinary Authority (AVA).

It follows an outbreak of avian influenza caused by the low-pathogenic H7N9 virus. This virus usually causes a milder illness in poultry than the highly pathogenic H5N1 strain.

But cases of both H5 and H7 strains must be reported to the World Animal Health Organisation as they could develop into highly pathogenic avian influenza viruses and cause serious outbreaks.

Kentucky's contribution to Singapore's poultry imports is low: In the 16 months before the suspension, 348.2tonnes of frozen poultry from the US state arrived here.

Last year, Singapore imported 165,278tonnes of chicken. The live chickens came mainly from Malaysia, and most of the frozen ones from Brazil.

But not all poultry and poultry products from the US are affected by the import suspension. Those from states that are free of avian flu are exempted. Similarly, heat-treated poultry products from Kentucky are not affected as heat treatment kills the avian-flu virus.

The AVA said on Wednesday it will continue to monitor the situation closely and take additional measures if other US states are hit by the outbreak.