"The strongest signal that can be sent is repatriation as quickly as possible," Doris Meissner, commissioner of the US Immigration and Naturalisation Service, told a news conference in Beijing.

Chinese migrants rescued from a rusting boat off Canada's coast

"That sends the message back to the home community that taking this risk and paying these amounts of money is not going to pay off."

Ms Meissner is in China to try to improve co-operation with Chinese officials on the issue.

"The amounts of money, the level of organisation, and the level of criminality, extortion and abuse that is involved in Chinese smuggling put it in a category that is [unique]", she said.

Ms Meissner stressed that, as new routes emerged and illegal migrants travelled in ever smaller groups, greater efforts were needed to dissuade Chinese people from leaving their homes in the first place.

Lorry deaths

Human trafficking from China has been the focus of international attention since the horrific deaths last month of 58 illegal Chinese immigrants smuggled into the UK in a lorry.

In Shanghai, China's largest city, police uncovered 976 illegal emigration attempts and arrested 1,013 suspects in 1999 - almost twice the number of arrests made in the previous year.

All but gone is the crude but common method of packing migrants into decrepit boats for long sea voyages ending in night-time landings along the US coastline.

No such vessels have been found this year, though some immigrants have been found in cargo ships docking at West Coast ports.

Faced with tighter law enforcement and greater vigilance, people-smugglers now take migrants out of China overland or by air to Europe and South and Central America.

Small groups typically enter the US through major airports, using doctored passports that are recycled and sold to other hopefuls.

So far this year, US officials have repatriated 2,700 Chinese arriving at airports, and the number is expected to reach 4,000 by the end of the year.

The incentives for Chinese smugglers are huge.

A one-way ticket to the United States from China by illegal means is estimated to cost as much as $50,000 - an immense amount by Chinese standards.