Brazil's government said Friday it will sue mining giants BHP Billiton and Vale for $5.2 billion in clean-up costs and damages after the deadly collapse of a waste water dam at an iron-ore mine.

Environment Minister Izabella Teixeira said a lawsuit would be filed demanding that the companies and mine operator Samarco, which they co-own, create a fund of 20 billion reais. The money would go to environmental recovery and compensation for victims.

"There was a huge impact from an environmental point of view," Teixeira said at a press conference in the capital Brasilia.

"It is not a natural disaster, it is a disaster prompted by economic activity, but of a magnitude equivalent to those disasters created by forces of nature."

The suit will be filed on Monday, Attorney General Luis Inacio Adams said.

At least 13 people died and some 11 remain missing from the flood of mud and waste water triggered by the breaking dam at the Samarco iron ore mine near Mariana in southeastern Brazil on November 5.

The deluge swept down the River Doce to the Atlantic, sparking claims of major contamination, although the mining companies insist there is no serious pollution.

The fund being demanded by the government would dwarf initial estimates by Deutsche Bank that a clean-up could cost about $1 billion.

Adams said that the companies would be asked to pay the amount out gradually, as a percentage of their profits.

"The measure should guarantee long-term financing for actions to revitalize the (river) basin," Adams' office said in a statement.

- Cooperation or denial? -

Adams said he hoped the powerful corporations -- BHP Billiton is the world's biggest miner and Vale is the world's biggest iron ore specialist -- would cooperate with the government. Both have said they want to meet their obligations.

"The scale of the damage is very big but the companies have announced measures that show they are interested in repairing their image," Adams said.

Teixeira described the environmental impact as devastating and difficult to repair.

"What was lost there is lost. The biological chain that was broken will not be put back together in any way as it was before. We have to create conditions so that nature establishes new ecological conditions," she said.

Earlier Friday in Rio de Janeiro, Vale announced a compensation fund, but did not give figures. Executives also sounded a defiant note, rejecting allegations that the River Doce has been badly polluted.

Vania Somaville, director of human resources, health and safety at Vale, told a press conference that lead, arsenic, nickel and chrome had been detected at some points along the river.

However, Somaville argued that the potentially dangerous contaminants were not carried there by the waste water from the mine.

"They were (already) there at the edges or in the bed of the river" and were disturbed in the flood, she said.

"The good news is that these materials did not dissolve in the water" and are now diminishing, she said.

This was in stark contrast to a report by two UN experts on Wednesday accusing the corporations and the Brazilian government of failing to respond to a toxic disaster.

The UN's special rapporteur on human rights and the environment, John Knox, said the equivalent of "20,000 Olympic swimming pools of toxic mud" spewed into the River Doce.

- CEO on the defensive -

Vale's CEO, Murilo Ferreira, has been criticized by environmental activists for what many saw as his slow response to the disaster and his attempt to distance himself from the tragedy by saying that Vale was only a shareholder in Samarco.

He told journalists Friday in a breaking voice that "the disaster has been extremely painful" for him and other executives.

"My soul is saddened and disturbed... We are very worried that there are 5,200 people who don't know what the future holds," he said, referring to the many jobs suspended in and around Samarco after the accident.

However, Ferreira once more sought to draw a distinction between Vale and the Samarco operation, saying that help was being offered only out of "solidarity."

"In four years I was never at the Samarco offices in Mariana," he said. Until the accident "I didn't know them... We don't know who their clients are or their prices."