In a televised address to the national on Tuesday evening, Kenyatta who also lost close family members said suggestions by intelligence analysts that one British woman and two or three Americans may have been involved could not be confirmed immediately.
"We cannot confirm the details at present. Forensic experts are working to ascertain the nationalities of the terrorists," Kenyatta said.
He praised the country's security forces for their dedication and professionalism that ensured the success of the operation, saying the officers' efforts exemplify the national values in action. He also saluted national leaders who stood together to reassure the nation that Kenya is one, indivisible national family.
"For sharing the nation's pain and anxiety, and for reaffirming the core principles of leadership, you have encouraged the nation. Let no one amongst us ever be blamed for dividing the people of Kenya," he said.
"The people of Kenya thank you. The operation to contain terrorists, pacify and stabilize our region and continent continues, and there will be opportunity to consult and cooperate in future."
Noting that terrorism is a global problem that requires global solutions, Kenyatta said Kenya will stand with its friends in tackling the evil.
He disclosed that forensic teams are still at the scene of the tragedy and will put together a final report with the confirmed death toll at the completion of their investigations.
President Kenyatta noted that the attack has strengthened and renewed Kenyans' resolve to live as one strong, open, stable, democratic and prosperous republic, where people of all races, cultures and faiths pursue happiness together.
In the confrontation with the terrorists at the Westgate mall 61 civilians and six security officers lost their lives. Five terrorists were killed and 11 suspects are in custody.
"Let us work in unity, in the spirit with which we defeated the monster of terrorism, to heal the wounds inflicted on us, and to confront the obstacles in our way to prosperity," Kenyatta said.
"As we put this tragic period behind us, let us stay true to who we are. Our attackers wished to destroy the essential character of our society. They failed. Kenya endured. Kenya endures."