Whitman said Malik was held at a US military facility, not a secret CIA prison, and was interviewed by US law enforcement before being sent to Guantanamo over the weekend.
"He is a one of these support figures in the al-Qaeda East Africa network. He knows some very important people"
Abdul Malik is the first detainee to be transferred to Guantanamo since September 2006, when 14 al-Qaeda suspects arrived from secret US prisons overseas.
Whitman said Abdul Malik was considered "dangerous" but not of "high-value", a term US officials use for captured suspects who have a significant effect on al-Qaeda operations and are capable of providing high-quality intelligence.
"He is a one of these support figures in the al-Qaeda East Africa network. He knows some very important people," another unnamed American official said.
Kenya has rounded up scores of suspected Islamist fighters and supporters since a war ended a six-month Islamist rule of Mogadishu and southern Somalia.