"Those reasons must be convincing or else we're going to take him to task," he said.
"There is no need for the army in Marikana. There was never a need for the army in Marikana. After the killing of 34 people by police we should have called for the disarming of police and the disarming of those civilians."
Malema was speaking at a hastily convened press conference in Sandton on Tuesday, a day after being prevented from addressing miners in the North West by police.
This came shortly after Zuma called for a crackdown on incitements to violence in the mining sector.
Malema was manhandled into a car, then accompanied to the highway by a cavalcade of police, and followed out of town by a police helicopter.
He told reporters at the briefing police had threatened to "isolate and shoot" him before running him out of town.
"What was disturbing to me was the chopper. The chopper accompanied me from Marikana to Pretoria. You can laugh about it but that's taxpayer money. To fly a chopper is very expensive," he said.
State of emergency
He denied inciting violence during his visit.
"I have not said anything so far. Leave me to say things of inciting violence then charge me with those things," he said.
"Sometimes we engage robustly, you think we are fighting, we are not. Were just looking for a long-lasting solution to the crisis facing our people."
The expelled youth league leaders, including Malema, Floyd Shivambu and Sindiso Magaqa – who now refer to themselves as the Economic Freedom Fighters – have objected to the "de facto state of emergency declared by the security cluster" at the end of last week.
On Friday, government announced that it would no longer tolerate illegal gatherings of miners and would move to disarm striking miners. This was followed by a raid on hostels, and a standoff with miners who had planned a protest march to a police station in Rustenberg.
Malema said there was "an illegal undeclared state of emergency" and that this was dangerous because unlike a declared state of emergency, which must end within 21 days or be renewed, there was no telling when it would end.
Zuma a 'liability'
Malema also used the opportunity to criticise Zuma for his lack of leadership. He called Zuma "a proponent of tribalism" who would "plunge the country into a deeper crisis".
"He is a liability to this country and the African National Congress," he said.
"Since Jacob Zuma took over leadership of the South African state, we have seen the introduction of dictatorship and extremely intolerant forms of leadership. Because of his inability to persuade and politically convince those that disagree with him, he has resorted to usage of force and coercion in his leadership style," he said.
Malema said he had intervened in the mining crisis because he had been called on to do so by miners, and because "it was clear political leadership in this country will not provide leadership except the killing of mine workers".
Malema praised former president Thabo Mbeki – whom he helped oust from the leadership of the ANC at Polokwane in 2007 – as one of the outstanding leaders produced by the ANC over the years, and that he regretted helping to get Zuma elected.
"It was a terrible mistake and we regret it. It was a bad idea from the onset. Those decisions were taken out of anger [but] to have him as president until 2014? You're extending trauma," he said.
Dismisses threats of death, arrest
"Jacob Zuma is inherently insecure and forever threatened by our presence," he said.
He said that the "police state" must be condemned and rejected for silencing ordinary South Africans, adding "today it might be happening to us, and tomorrow it will be happening to all other South Africans".
Malema said he had it "on good authority" that there are threats against his life and that a "death warrant" had been issue against the Economic Freedom Fighters.
However, he said these had not been reported to the police.
"[We] did not report it to the state because we do not trust the state and also we've lost confidence in the police system, the way it's being run and politically interfered with," he said.
He dismissed reports that he is due to be arrested in the coming weeks saying, "The Hawks have been arresting me every weekend for the past three years.
"Every time I embark on a political programme, I know the following Monday [headlines will say] 'Malema to be arrested'."
Earlier this month a senior government official told the M&G the Hawks were ready to arrest Malema on charges of fraud and corruption related to tax liabilities and his involvement in tender fraud.
Malema also used the opportunity to slam the South African Broadcasting Corporation (SABC), which he said has "been reduced into [sic] a praise singer of Jacob Zuma".
Last week SABC staffers alleged they had been banned from reporting on Malema in the news.
The public broadcaster denied the allegations, saying it had instead called for "more responsible and in-depth reporting on the issues".
Threatens to sue ANC
Malema said he still has hopes his expulsion will be overturned at the ANC's elective conference in Mangaung later this year. If this failed, he would rejoin the ANC as a new member.
"If the ANC declines my application it will have to explain to court why. Why am I being isolated and discriminated against?" he said.
He said reapplying to the party would be done through his branch, which would make the decision whether to accept or decline it, and added he did not foresee his branch in Seshego declining his application as it has been inviting him to general meetings despite his suspension.