The US Supreme Court is the highest legal authority in the nation
The US Supreme Court has cleared the way for a lawsuit against major international companies accused of aiding South Africa's apartheid system.
The court said it could not intervene over the case because of a potential conflict of interests.
Four of the nine justices had ties to the firms involved and could not rule on the case, it said.
By law, at least six justices must sit in order for the Supreme Court to hear a case.
As a result, the court could only uphold a lower court ruling allowing a lawsuit to go ahead against firms accused of aiding South Africa's apartheid system.
Apartheid was a policy which enforced a separation of the nation's races from the 1940s until the early 1990s.
The victims are seeking damages reported to be worth more than $400bn (£205bn).
Among the corporations accused in the lawsuit are oil firms BP and Exxon Mobil, banks including Citigroup and Deutsche Bank and multinationals like General Motors and Ford.
The plaintiffs bringing the lawsuit argue that the corporations violated international law by assisting South Africa's former apartheid government.
An appeals court in New York ruled last year that the lawsuit, being brought under a US law which allows foreigners to sue in US courts over breaches of international law, could proceed.
The Bush administration, the current South African government and business groups had sought the intervention of the Supreme Court.
They argue that the legal action is damaging to international relations and may threaten South Africa's economic development.
However, the court's hands were tied by federal laws requiring at least six of the nine justices to hear any case.
Chief Justice John Roberts and Justices Stephen Breyer and Samuel Alito all had to sit out because they had financial interests in some of the companies concerned.
According to the Associated Press news agency, Mr Roberts owns stock in Hewlett Packard, Mr Alito has shares in Exxon Mobil and Mr Breyer has stock in Colgate-Palmolive, Bank of America, IBM and Nestle.
Justice Anthony Kennedy sat out the case because his son works for Credit Suisse, another company concerned.