UPDATE 4-Bolivia may scrap Glencore, Pan American contracts
* Govt says would be "recovery", not nationalization
* Recision could be decided later this month
* Unions proposed returning mines to state control (Updates with details on time frame, output figures, context)
By Claudia Soruco and Carlos Quiroga
LA PAZ, April 14 (Reuters) - Bolivia's leftist government may rescind concessions on four mines run by Glencore [GLEN.UL] affiliates and Canada's Pan American Silver PAA.TO(PAAS.O: Quote), the Andean country's mining minister said on Thursday.
Mining unions are asking the state to "recover" the silver, zinc, lead and tin mines currently operated by private firms, which would be in line with President Evo Morales' drive to regain control over key natural resources since 2006.
Mining Minister Jose Pimentel said state-run Bolivia Mining Corp (COMIBOL) would assume control of the mines if the concessions were rescinded, a move described as "recovery, not nationalization" that could happen before May 1.
The decision would affect Swiss commodity trader Glencore's Porco, Colquiri and Bolivar mines, as well as Pan American's San Vicente mine.
Pimentel said the government did not plan to target mining projects that have been private investments from the start, such as San Cristobal, the country's largest silver mine, owned by Japan's Sumitomo Corp (8053.T: Quote). Continued...