Thai authorities plan to cut water, electricity and food supplies to thousands of protestors occupying Bangkok's main shopping district for nearly six weeks and said they might resort to force if they fail to disperse.

The threats follow the unravelling of a peace plan proposed last week by Prime Minister Abhisit Vejjajiva to end a political crisis that has killed 29 people, paralysed parts of Bangkok and slowed growth in southeast Asia's second-biggest economy.

Leaders of the mostly rural and urban poor protestors remained defiant, refusing to leave their encampment in Bangkok's main shopping district.

'We will die here if we must. Your threat will not work,' Nattawut Saikua, a protest leader, told cheering supporters.

Talks to resolve the impasse have been called off and a proposed November election scrapped, said Korbsak Sabhavasu, the prime minister's secretary-general.

At midnight, authorities will shut off power, cut supplies and seal entrances to the protest site, said army spokesman Sansern Kaewkamnerd at the government's crisis control centre.

'The measures to cut water and power are the first measures. If the protest does not end, we have to fully enforce the law, which may involve using force to reclaim the area,' he said.

Severing supplies presents a huge logistical challenge in an area crowded with hotels, embassies, businesses, high-end apartments and two public hospitals. The protestors said they would survive with their own power generators and food sources.

The protestors are mostly supporters of ex-premier Thaksin Shinawatra who was ousted in a coup in 2006.

The Prime Minister's tone has hardened in the past two days and late yesterday he said the cabinet had decided the security forces needed to 'take measures' quickly and the protestors had to leave today, Wednesday.