Brown made a brief visit to the provincial capital of Helmand during the weekend to congratulate British, Afghan and NATO forces for their early successes in Operation Moshtarak.
Brown during his visit hailed the expansion of the Afghan forces, seen as a foundation for the new war strategy outlined by U.S. President Barack Obama in December.
"The Afghan army is already rapidly expanding. Around 7,000 Afghan troops are being trained each month," Brown said. "But we also need a strong Afghan police force to create enduring security. That is a key challenge for the next phase."
International forces are keen to highlight the growing capabilities of their Afghan counterparts in Helmand.
U.S. and NATO military planners said the so-called clear, hold and build strategy employed in Helmand is the model for future operations in Taliban stronghold Kandahar.
"I think you'll see Kandahar will closely follow but central Helmand had to come first," Michele Flournoy, the U.S. undersecretary of defense for policy, told the Senate Armed Services Committee in a February briefing.
Afghan and international forces launched Operation Moshtarak in Helmand province Feb. 13.