KUALA LUMPUR, September 15, 2008 (AFP) - Malaysian opposition leader Anwar Ibrahim held a mass rally Monday, on the eve of a deadline he has set to seize power with the help of defecting government lawmakers.

Anwar arrived to rapturous applause from up to 7,000 supporters gathered at a Kuala Lumpur stadium which echoed to chants of 'Reformasi' -- the opposition battlecry of 'Reform'.

Officials from his Keadilan party said he would make a speech that could shed light on his plans to topple the ruling Barisan Nasional coalition, which has dominated Malaysian politics for half a century.

But there were mixed messages over whether he will Tuesday declare he has the support of the 30 lawmakers he needs to form a new administration, and formally challenge Prime Minister Abdullah Ahmad Badawi.

Tian Chua, information chief of his Keadilan party, said the three-member opposition alliance had signed up enough defectors to form a simple majority in parliament and that Anwar wanted to meet with Abdullah Tuesday to inform him.

'We want Abdullah to assure us there will be no repressive force used, like involving the police or inviting the military to take control,' he told AFP.

Tian Chua said the opposition's push had been helped by a government crackdown Saturday that saw an opposition politician, a prominent blogger and a journalist detained under draconian internal security laws.

'Abdullah's final crackdown made people lose hope that he is ever going to be a liberal reformer, which he promised,' he said.

However, Keadilan vice-president Syed Husin Ali was more cautious, declining to specify how many defectors were on board and only saying that 'tomorrow the beginnings of the process will happen.'

'The whole process might take a month but it could be sooner,' he told AFP. 'You never know, he might announce something this evening. And tomorrow there will definitely be an announcement of something.'

Spirits were high at the stadium, which was emblazoned with Malaysian flags and posters demanding the release of the opposition politician and the blogger -- who remain in custody after the journalist was freed.

'I am sure Anwar will form the next government, as we the people have spoken as we want to see a new Malaysia led by Anwar,' said 54-year-old taxi driver Yaacob Ismail.

The opposition made surprise gains in March general elections, seizing control of five states and a third of parliamentary seats in the biggest challenge ever faced by the coalition.

'My entire family is here, we want to tell Abdullah to leave now. I am confident Anwar will form a new government soon. We are very excited. I can't wait,' said Juliette Ramasamy, a 24-year-old student.