US Attorney David Kelley was scheduled to hold a news conference with an FBI official on Thursday to announce the unsealing of the indictment of a Texas businessman, a Bulgarian and a British citizen.

David Chalmers Jr, his oil company Bayoil of Texas, and Bayoil Supply & Trading Ltd, based in the Bahamas, face federal criminal charges as part of the scheme to pay millions of dollars in secret kickbacks to Iraq.

Two others also were charged in the plot: Ludmil Dionissiev, a Bulgarian citizen living in Houston, and John Irving, a British citizen, according to the indictment unsealed in US District Court in Manhattan.

The indictment charges that the kickbacks were paid so the Bayoil companies could participate in selling Iraqi oil under the UN programme.

The bribes involved funds otherwise intended for humanitarian relief, Kelley said in a statement.

In addition, Kelley was to unseal a criminal complaint that charges a South Korean citizen with conspiracy to act in the US as an unregistered government agent for the Iraqi government's effort to create the oil-for-food programme, the statement said.

Findings of the independent investigation, expected in mid-summer, will likely lead to dozens of criminal prosecutions by legal authorities in various countries for bribery, sanctions busting, money laundering and fraud, officials told The Associated Press last month.

After two interim reports focusing on key UN figures, the investigation is tackling broader issues, including the Security Council's oversight of the $64 billion oil-for-food programme and Hussein's alleged attempts to use it to enrich himself and win political influence.

The US and other UN member states have refused to fully cooperate with investigators looking into corruption in the oil-for-food programme, blocking access to information about politically sensitive actions of Security Council nations.