It could be several years before global tourism recovers from the air attacks on the US, but the longer-term outlook remains upbeat, the head of the World Tourism Organisation (WTO) has said.

"It's very difficult to make an assessment, since it's the first time there has been an incident of such huge dimensions," Francesco Frangialli, secretary general of the 139-member intergovernmental organisation, said in an interview.

Long-term projections for international tourism, however, were unchanged.

"We shall come back on track in one to two years," he said.

Frangialli was in Seoul to attend a biannual general assembly.

The US military is in the midst of its biggest mobilisation since the 1991 Gulf War in response to the attacks, which left nearly 7,000 dead or missing.

Airlines worldwide have reported sharp declines in ticket sales, which have led to job cuts and service curtailments.

Frangialli said his organisation maintains its projection for international tourist arrivals to top one billion by 2010 and over 1.5 billion trips abroad by 2020.

"We're on a trend of rapid growth," he said.

The WTO said during the first eight months of 2001, global tourism was on track for an increase of 2.5 to 3.0 per cent. Barring widespread new developments, it predicted growth this year should come in at between 1.5 to 2.0 per cent.

Last year, the industry grew by 7.4 per cent and generated $476 billion, excluding airfares.

Frangialli predicted the global tourism industry will display its characteristic flexibility in coming months.

"Most travellers will shift to another part of the world. They may postpone their travels for a few weeks, but they will travel in greater numbers the following year," he said.