Washington has stepped up its avian flu screening programme to protect the USA from what it sees as the “increasingly likely” arrival of the H5N1 strain of the disease.

“By intensifying our monitoring of migratory bird populations, we increase the likelihood of early detection, which is key to controlling the spread of the virus in our domestic poultry,” said agriculture secretary Mike Johanns.

Testing migrating birds for H5N1 has been ongoing in the USA since 1998, he told journalists this week.

But given the recent global expansion of the disease and the onset of the spring migration, the time had come to increase the level of screening.

In 2006 the US department of agriculture will collect between 75,000 and 100,000 live and dead wild birds. A further 50,000 samples of water and faeces will be taken and analysed.

Priority will be give to the Alaskan and Pacific flyways, to pick up birds coming from the west.

This will be followed by the Central, Mississippi and Atlantic flyways.

US secretary of the interior Gale Norton said it was important to keep the threat of avian flu and a possible human pandemic in context.

But she added that it was “increasingly likely that we will detect the H5N1 strain of avian flu in birds within the US borders, possibly as early as this year”.

It was most likely to arrive via the Pacific Islands or Alaska.

Money for the enhanced surveillance programme will come out of the $29m (£16m) avian flu budget already approved by President Bush.