Poverty, profits and old farming traditions combined to spark massive Indonesian fires that have choked parts of Malaysia with noxious haze, in what officials describe as Southeast Asia's worst ecological crisis in years.

Slash-and-burn agriculture is not new to Indonesia, and its neighbors - particularly Malaysia - are fed up with Jakarta's failure to stop to it.

The fires, mostly set by plantation owners, logging companies and poor farmers, keep burning year after year on Indonesia's Sumatra island and its portion of Borneo.

The haze routinely drifts across the narrow Strait of Malacca to Malaysia and Singapore between July and October. ``We're up against tradition, up against poverty and plantation companies that do things their own way,'' said Ong Keng Yong, secretary-general of the Association of Southeast Asian Nations.

``It's a constant challenge for us to educate these people,'' Ong said. ``We have good enforcement measures, but when people get desperate, they find the easiest way and burn down areas.''

Indonesia has said it is doing its best to contain the latest fires, which have scorched up to 2,000 hectares of land in Sumatra's Riau province alone since August 2.

Malaysia has set up a team of 100 firefighters and 25 disaster management experts to send to Sumatra to help. But Indonesian President Susilo Bambang Yudhoyono, while saying he welcomed cooperation from his neighbor, has yet to give it a green light.

Only 400 people are now fighting the blazes, mostly with water buckets.

``It's humiliating to see the haze. We create problems for our neighbors over and over again,'' said Nazir Foead of the World Wide Fund for Nature Indonesia. ``Some [Indonesian] ministers want to stop this, but law enforcement agencies don't seem to take the issue seriously.''

Fires that raged for months in 1997 were the worst in decades. It was believed they would be a wake-up call for Indonesia after they destroyed 10 million hectares of forest, causing nearly US$10 million (HK$78 million) in economic losses.

The 10-country ASEAN bloc responded by forming a special haze task force, and signed a landmark 2002 agreement aimed at fire prevention. The agreement, praised by the United Nations as the first regional pact of its kind, looks good on paper. But Indonesia has never ratified it, and ASEAN can do little to force its hand.

Indonesia's neighbors, led by Malaysia, have used a mix of quiet diplomacy and blunt criticism to prod the country to ratify the pact and crack down on the illegal fires. But to no avail.

For plantation workers like Surip, in Riau's town of Duri, clearing land by fire has been a way of life for centuries. It is a cheap alternative to using land-clearing machinery.

Surip, who goes by one name, said workers at palm oil plantations light fires about three times a year to burn off tall grass and brush. He said he's never been warned by police or government that the practice is banned by law.

``We've been doing this for dozens of years,'' Surip said. ``It's not only me. There are dozens of workers, peasants, [and] land owners clearing their land.''

Economic factors explain Jakarta's reluctance in halting slash-and-burn agriculture, said Australian National University professor Luca Tacconi.

``If the Indonesian government stops these people from clearing the land, you would have huge economic costs to the country because this brings in a lot of money,'' said Tacconi.

The Center for International Forestry Research, a conservation group, urged the international community to ban agricultural development in peat lands - the source of much of the haze. It also asked Indonesia to provide economic compensation to land owners who agree to leave the land idle.