"We have confidence in the secretary-general," Powell said after a meeting with Annan at the U.S. State Department.
There are two investigations into alleged corruption at the U.N. oil-for-food program with Iraq in the 1990s under which Saddam Hussein was able to sell oil in exchange for food for his people. There have been questions raised over the role played by Annan's son Kojo who worked for a Swiss firm that was involved in the program.
"We're both deeply concerned about this matter," Powell said with Annan at his side.
Annan added, "The oil for food is something I'm concerned about and want to get to the bottom of."
Some U.S. lawmakers in Capitol Hill have called for Annan's resignation following allegation over his son's role in the program.
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