"I think we could get another 50,000 Afghan army personnel trained over the next year," Brown told the BBC from Helmand province, Afghanistan, where the majority of Britain troops are based.
"Stepping that up means that the Afghans take more responsibility for their own affairs," he said.
More than 200 British soldiers have been killed since the U.S.-led multinational military operation started in late 2001. Currently, there are approximately 9,000 British troops in Afghanistan.