* Neighbours fear Islamist resurgence in Mali's north
* AU wants robust force to support overstretched UN peacekeepers
* Initiative facing finance challenges
By Aaron Maasho
BAHIR DAR, Ethiopia, April 18 (Reuters) - Plans for a new African counter-terrorism force to support vulnerable U.N. peacekeepers in Mali, where militant Islamist groups are stepping up their activities, should be finalised by July, the African Union's special envoy to Mali said.
The government in Bamako and officials of the U.N. MINUSMA force in Mali have sought more help in combating al Qaeda-linked insurgents, who have become more active despite efforts by French, Malian and U.N. troops to quash them.
As the threat emerged in Mali from several Islamist groups, neighbouring West African states agreed in late 2014 to form a mission along the lines of a special U.N. brigade sent to eastern Congo in 2013.
Diplomats say a bid by the regional states - which include Mali, Burkina Faso, Chad, and Ivory Coast - to launch the force has been hampered by difficulties in harmonising it with other security initiatives and regional rivalries for influence.
"My judgment is maybe in three months, we should have a clear idea of what will be done and how it will be done," Pierre Buyoya, the special representative to Mali, told Reuters in the Ethiopian city of Bahir Dar during a conference on security.
"This terrorist threat is threatening not only Mali, but also the whole region. Northern Mali has become a base to attack Burkina Faso, to attack Ivory Coast, and maybe tomorrow other countries," he said in an interview.
French forces drove jihadists out of Mali's northern cities in 2013 but they have since regrouped, launching attacks such as one on a Bamako luxury hotel in November in which 20 people were killed.
In March, further south, fighters from al Qaeda in the Islamic Maghreb - the group's North African branch - shot swimmers and sunbathers before storming hotels in the Ivory Coast town of Grand Bassam, killing 19 people.
Critics say the 10,000-strong U.N. force's ability to bring peace to Mali is hamstrung by its lack of an aggressive counter-terrorism mandate, so it cannot hunt militants to pre-empt attack.
Buyoya said models such as those of the AU's AMISOM force in Somalia that is battling al Shabaab Islamists or the multi-national force tackling Boko Haram militants in Nigeria and neighbours were also being considered for the new mission.
The resurgence of Islamist groups such as the Massina Liberation Front (MLF) and al Qaeda-linked Movement for Unity and Jihad in West Africa (MUJWA) have also threatened to derail a Mali peace agreement signed by the government with Tuareg-led rebels last year, officials say.
Buyoya said a preliminary study on the new force had been drawn up by regional defence ministers and chiefs of staff.
"The big challenge now is commitment of partners for funding, because clearly the African Union does not have the means to fund this force," he said, without suggesting who would finance the new force. (Reporting by Aaron Maasho; Editing by Richard Balmforth)
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