* Security Council resolution needed to defer cases
* African Union: trials will distract leaders
* No request to defer Sudanese president's case
By Michelle Nichols
UNITED NATIONS, Oct 22 (Reuters) - The African Union and Kenya asked the U.N. Security Council on Tuesday to defer the trials of Kenya's leaders at the International Criminal Court for one year so they can deal with the aftermath of the Nairobi mall attack.
In a letter to the council obtained by Reuters, African leaders said the legal proceedings against President Uhuru Kenyatta and his deputy William Ruto "will distract and prevent them from fulfilling their constitutional responsibilities, including oversight for national and regional security affairs."
Kenyatta and Ruto face charges of crimes against humanity related to the violence that followed Kenya's 2007 elections, in which 1,200 people died. Both deny the charges and have tried to have the prosecutions adjourned or halted.
The AU requested that their trials be deferred "in order to provide them with the time required for the enhancement of the efforts aimed at combating terrorism and other forms of insecurity in the region."
At least 67 people were killed when al Qaeda-linked group al Shabaab attacked Nairobi's Westgate shopping centre last month.
In a separate letter, Kenya's U.N. Ambassador Macharia Kamau said that when considering the deferral request, the 15-member Security Council should take into account the "threat to the peace, breach of the peace or act of aggression likely to transpire in light of the prevailing and continuing terrorist threat existing in the Horn of and Eastern Africa."
Council envoys have said they would consider any AU request but note that the council had turned down a deferral request in 2011 and rejected a request in May for the cases to be terminated because the council had no such power.
The Security Council can defer ICC proceedings for one year under Article 16 of the Rome Statute that established The Hague-based court a decade ago. The council would need to adopt a resolution to take that step.
The AU and Kenyan letters to the council come 10 days after African leaders called for the prosecutions of Kenya's and Sudan's presidents by the ICC to be halted.
The AU letter to the Security Council on Tuesday did not request a deferral for Sudanese President Omar Hassan al Bashir, who faces charges of genocide. Unlike the Kenyan politicians, who have so far cooperated with the ICC, Bashir has defied an arrest warrant, deepening his nation's alienation from the West.
Ruto's trial started last month and Kenyatta's trial is due to start in November. The cases have stirred an increasing backlash against the court from some African governments, which regard it as a tool of Western powers.
ICC judges on Friday excused Kenyatta from "continuous presence" at his impending trial. It is the court's most high-profile case since it was established and the first against a sitting president.
In May the AU backed a request by Nairobi for the trials to be referred back to Kenya on the ground that the ICC hearings risked raising ethnic tensions and destabilizing its economy. (Reporting by Michelle Nichols; Editing by Xavier Briand)