No official announcement of the postponement was made, but local media quoted home ministry sources as saying an amnesty period would be extended and one official told AFP he had not received a directive to begin the sweep, due to begin Tuesday.

"We are awaiting the green light to launch the nationwide crackdown," Mahadi Arshad, director-general of the People's Volunteer Corps told AFP.

Half a million members of the corps, an organisation of uniformed part-timers who have some policing powers, were due to be deployed to help hunt down the illegal immigrants.

"So far we have not launched any raids today. But we are on standby," he said.

Tuesday was a public holiday in Kuala Lumpur and government officials were not immediately available for comment.

Indonesia, whose citizens make up most of the hundreds of thousands of illegal immigrants in Malaysia, had appealed for an extension of a three-month amnesty, ambassador K.P.H. Rusdihardjo told The Star newspaper.

He said Indonesian state secretary Usril Ihza Mahendra would arrive in Kuala Lumpur later Tuesday to deliver a letter from President Susilo Bambang Yudhoyono to Prime Minister Abdullah Ahmad Badawi.

In Manila, the Philippine Star newspaper said the Philippine government had asked Malaysia to extend the amnesty by a month to accommodate the estimated 170,000 Filipinos who failed to take the chance to leave the country legally.

The UN refugee agency had also requested an extension of the amnesty, an official said.

"We have asked Malaysia to delay any operations against migrants for a period of three months," Volker Turk, head of the UN High Commissioner for Refugees (UNHCR) in Malaysia, told AFP.

He said Mahadi's remarks were an indication that the government had postponed the controversial plan.

"It seems it has been called off. We welcome Malaysia's humanitarian gesture," he said.

Turk added that the UN refugee body had in early January advised countries not to deport migrants back to areas devastated by last month's tsunami. Many illegal immigrants are from Indonesia's Aceh province, the area worst hit by the giant waves.

An estimated 400,000 illegal immigrants took the opportunity to go home during the three month amnesty without facing any penalty, leaving at least the same number still in the country, officials have said.