Former Kenyan minister Nicholas Biwott has been banned from entering the United States for alleged corruption.
Mr Biwott was Kenya's most powerful politician under Mr Moi
Washington revoked his visa on Wednesday under a new law but refused to disclose the evidence against him.
Mr Biwott, 63, was considered one of Kenya's most powerful politicians during the reign of former President Daniel arap Moi.
He was one of several ministers named in an inquiry into the siphoning of $700m of government funds.
The decision is a body blow to the image of the MP who is locked in a battle for control of the Kanu (Kenya African National Union) opposition party.
He was not available for comment on the ruling.
Section 212 of the American Immigration and Nationality Act, introduced in January, gives authority to "suspend entry as immigrants or non-immigrants of persons engaged in or benefiting from corruption".
A US State Department official said: "Due to confidentiality of visa records, as provided for in the Immigration and Nationality Act, we are not able to provide further details concerning this matter."
A spokeswoman for the department said any individual denied a visa is entitled to re-apply but the department could not say whether it would be accepted.
Mr Biwott was among several ministers close to Mr Moi named in a parliamentary committee into corruption in 2000.
The report said corrupt officials in the provincial administration had defrauded the government of some $700m between 1990 and 2000.