BEIJING (Reuters) - China has reported another outbreak of bird flu, a senior U.N. official said on Tuesday, as fears grow across the world of a possible future pandemic. 

The World Health Organization has said the H5N1 strain of bird flu is endemic in poultry in China and across much of Asia, and it may only be a matter of time before it develops the ability to pass easily from human to human. 

The latest outbreak, among farm geese, was in the village of Liangying, near Tianchang in the eastern province of Anhui, Noureddin Mona, of the U.N. Food and Agriculture Organization, told Reuters. 

He said China's Ministry of Agriculture had told him on Monday 2,100 birds had been infected, 550 had died and 45,000 had been culled. 

"We are highly concerned about this," he said of the outbreak, adding that the area had been sealed off in a radius of five km. He said there were no suspected cases of human infection. 

China's sheer size and its attempts to conceal the emergence of the SARS virus in 2003 have prompted fears among some experts that it has had more bird flu cases than officially recorded. 

The latest outbreak occurred in a densely populated farming province 300 km from Shanghai -- and on the shores of Lake Gaoyou, where duck and geese farmers mingle with wild birds. 

"STRONG COMMITMENT" 

But experts and U.N. officials said they believe China is better prepared and more open than in 2003. 

"I think that, now, China is unlike (it was) during SARS," Mona said. "They are highly concerned and have no option but to report." 

Julie Hall, a Beijing-based WHO official who oversees response to the disease, said China last week provided WHO

scientists with genetic information about a previous outbreak in far western China in July -- a step experts said China should have taken months ago. "There's now a strong political commitment to sharing the information in a timely way," she said. 

Local governments across China have set up monitoring stations to check poultry and people, according to Chinese media reports. Officials were also offering compensation to farmers who reported suspected infections among their poultry, said Mona. 

But experts and officials said they remain concerned about the risks of migratory birds across Asia spreading the bird flu virus further afield to poultry on small farms and then possibly into people. "This presents a very difficult, high-risk situation," said Mona. 

"Migratory birds have played a role in the big jumps the virus has made," said Roger Morris, an expert on the spread of the disease at Massey University in New Zealand. "They're seeding new sites and then it spreads through domestic birds." 

Mona said Chinese officials did

not mention any possible outbreak among wild birds around Tianchang. 

The Ministry of Health denied a Hong Kong newspaper report that China would close its borders if a single case of human-to-human transmission of bird flu occurred. "The report is inaccurate," a ministry official told the China Daily. 

Since an outbreak in late 2003 in South Korea, the deadly H5N1 strain of avian influenza has killed more than 60 people in four Asian countries and reached as far west as European Russia, Turkey and Romania, tracking the paths of migratory birds. 

Morris, the disease expert, said a mutation allowing the virus to jump from human to human was most likely to emerge in Asia. 

Farmers in Asia often live close to birds and livestock, making it much easier for humans -- an ideal mixing bowl for mutation -- to be infected with the virus to start with. 

"Europe is minor sideshow to what is really going on," he said. "We've got to block the link between wild birds and domestic birds."