* Mali says nations to establish joint desert force
* Pledge to test steps towards regional cooperation
By Sadio Kante
BAMAKO, May 20 (Reuters) - Mali, Mauritania, Niger and Algeria will set up, within 18 months, a joint force of up to 75,000 soldiers to secure their shared Sahara-Sahel desert zone, Mali's foreign minister said on Friday.
The four nations are struggling to control the zone, where al Qaeda's North African wing has stepped up attacks and is operating alongside smugglers, rebels and local criminals.
A joint command centre has been established in Tamanrasset, in southern Algeria, but regional rivalries and the lack of trust between the countries have long stymied a coordinated regional approach European nations and the U.S. have called for.
"The number of soldiers in the force tasked with fighting terrorism will increase to ... 75,000 in the next 18 months," Malian Foreign Minister Soumeylou Boubeye Maiga said, according to a text of a speech given to Reuters.
Maiga, who was speaking at a meeting in Mali, also stressed the need to tackle "trans-national organised crime".
Leaders from the four nations gathered in Mali to look at security issues, including the fall-out from the conflict in Libya, which experts say has increased the access to arms. [ID:nLDE7400GO]
Al Qaeda's regional faction, known as AQIM, has grabbed headlines, largely by kidnapping Westerners for large ransom payments but also carrying out a handful attacks on regional armies.
Four Frenchmen and an Italian woman are currently being held by the group.
But broader criminality, linked to smuggling, corruption and banditry is seen as a high risk in poor desert communities, especially in Mali and Niger, where there are lingering complaints about marginalisation.
Abdelkader Messahel, Niger's foreign minister warned: "No battle against criminality on this scale is possible without tangible economic development also being put in place."
The tourists who once travelled into the desert regions have stopped coming while mining firms operating in the region have had to take added precautions and complain of higher security costs. (Writing by David Lewis; Editing by Jon Boyle)