* Ban presents three logistical support options for Mali war
* UN Security Council authorized African force in December
* Ban says UN combat support could put UN personnel at risk (Adds comment from French U.N. ambassador)
By Michelle Nichols and Louis Charbonneau
UNITED NATIONS, Jan 22 (Reuters) - U.N. chief Ban Ki-moon warned the U.N. Security Council against requiring the world body to provide logistical support for combat military operations in Mali, saying such a move would put U.N. civilian staff throughout the region at "grave risk."
In December, the 15-member Security Council authorized the deployment of an African-led military force to help defeat al Qaeda and other Islamist militants in northern Mali and called on the secretary-general to submit funding options.
"The situation in Mali is critical. Terrorist organizations threaten the way of life of the Malian people, and even the existence of the state," Ban told the Security Council in a letter on Sunday to the council, obtained by Reuters on Tuesday.
The planned 3,300-member African force - known as AFISMA - was not expected to be ready until at least September, but France asked that it be accelerated after Paris launched air strikes and deployed some 2,150 ground forces this month to halt a surprise Islamist offensive toward the Mali capital Bamako.
U.N. Undersecretary-General for Political Affairs Jeffrey Feltman briefed the Security Council on Mali on Tuesday and said that, as of Sunday, 855 troops had been deployed for the African force from Benin, Nigeria, Senegal, Togo and Niger.
"The capabilities of the armed groups occupying northern Mali have proven to be strong, as they are better equipped and trained than initially anticipated," Feltman told the council.
"There is general agreement amongst key stakeholders in Bamako that the envisaged AFISMA strength of 3,300 personnel needs to be increased in order for it to engage effectively in offensive operations and enhance force protection," he said.
Ivory Coast U.N. Ambassador Youssoufou Bamba, whose country holds the chair of West African regional body ECOWAS, told the Security Council that the size of AFISMA could be doubled.
In the letter, Ban presented three options for funding AFISMA: bilateral logistical support without U.N. funding; complete U.N. logistical support for all phases of the operation that would be funded through states' mandatory U.N. contributions; or bilateral support for combat phases, followed by U.N. support for deployment and stabilization.
ISLAMIST ATTACK FEARS
However, Ban tried to steer the council away from approving the second option of full U.N. logistical support.
"If the United Nations were to provide logistics support to military forces engaged in an offensive operation, it would place civilian United Nations personnel at grave risk, and undermine their ability to carry out their current tasks in the region," Ban wrote.
The perceived neutrality of U.N. staff across the Sahel region - a belt of drought-stricken land spanning nearly a dozen impoverished countries on the southern rim of the Sahara - would be undermined if the world body supported the Mali offensive.
The crisis in Mali has already exacerbated a humanitarian crisis in the Sahel.
"A dramatic shift in the posture of the (U.N.) organization would have a further negative impact on its ability to implement essential mandates in the humanitarian, development and human rights areas," he said.
The aim of the intervention is to prevent northern Mali from becoming a launchpad for international attacks by al Qaeda and its local allies in North and West Africa. Fears of this increased sharply after a hostage-taking raid by Islamist militants last week on a gas plant in Algeria.
Chadian forces advanced towards the Malian border on Tuesday as an African troop deployment and a U.S. military airlift swelled international support for French operations against the Islamist rebels.
"This operation has been a success so far. Its primary goal has been met - the terrorist offensive against the south has now been stopped," French U.N. Ambassador Gerard Araud said on Tuesday, adding that France wanted the Malian and African forces to take responsibility for the operation as quickly as possible.
Ban said that if the council decided to approve the second option of full U.N. logistical support for the African force in Mali, it would take a minimum 120 days "to implement the full range of services under the logistics support package."
"The acceleration of the deployment of AFISMA clearly poses great operational challenges," said Ban, adding that "significant external support" was urgently required for the training, equipment, combat logistics and other needs.
Once viewed as an example of democratic progress in Africa, Mali was plunged into chaos in March by a coup that toppled the president and left a power vacuum that was quickly exploited by rebels to seize the country's desert north. (Editing by Stacey Joyce)