Botswana's Debswana has cut its diamond output forecast for 2012 by nearly 17 percent to 19.9 million carats because of a weak global market, a senior company official said.

Production disruptions at the company's flagship Jwaneng mine, including a four-week stoppage after an accident earlier this year, had also affected output, managing director Jim Gowans said.

Debswana, a joint venture between De Beers and the government of Botswana, produced 22.8 million carats last year. Botswana is the world's biggest diamond producer, making its economy vulnerable to switches in global demand trends.

Subdued demand from key markets such as China has seen production stagnate, putting a lid on growth prospects in the landlocked southern African nation that depends on mining for about a third of its economy.

The government expects economic growth to slow to 3.5 percent this year from 8 percent in 2011 due to the lower mining output。