Kabul , Afghanistan ( CNN ) -- NATO 's goal of ending combat operations in Afghanistan and leaving security in local hands by the end of 2014 is realistic , British Prime Minister David Cameron said Tuesday on his second visit to the nation in 2010 . `` It 's challenging , but it is achievable , '' Cameron said . `` What I see is actually some grounds for cautious optimism . '' Cameron cited the continued training of the Afghan National Army and the nation 's police force , noting 500 police officers are coming out of a British-run police academy every eight weeks . `` There are more markets open , more children going to school , local governors providing legitimate governance with the local population rejecting the brutal shadow ( of the ) Taliban regime , '' Cameron said during a joint news conference with Afghan President Hamid Karzai . In the same conference , Cameron addressed the international WikiLeaks situation . WikiLeaks , which facilitates the anonymous leaking of secret information , has been under intense pressure from the United States and its allies since it began posting the first of more than 250,000 U.S. State Department documents on November 28 . `` I do n't want the WikiLeaks to come between our strong relationship . Some of what was referred to was the fact that there was not enough troops in Helmand province in the past , and that is certainly true , '' Cameron said . `` It 's clear that we did not have enough troops in Helmand to actually deliver the security that was necessary . '' But Cameron added , `` I think you can now see on the ground with 20,000 U.S. Marines , with some 10,000 U.K. forces , you really can see a density of forces that are able to deliver security to the vast majority of the people . '' Karzai , who said WikiLeaks documents have `` some truth and some not so truth in them , '' replied in a less serious tone . `` On a lighter side , you should wait for the WikiLeaks from Britain so our conversation with Britain 's leaked on America , '' the Afghan president said , drawing laughter from the British prime minister . `` We 're very nice about that , just to be clear , '' Cameron said . `` Most of the time , '' Karzai quipped . NATO has some 150,000 troops in Afghanistan , pressing the fight against the Taliban and al Qaeda . About 9,500 of the forces are British , according to the country 's Ministry of Defence . During the joint press conference , Karzai expressed his gratitude to Britain . `` Britain has been as steadfast supporter of Afghanistan and of the Afghan people , '' Karzai said . `` Britain has contributed in the sacrifice of its soldiers , of blood and of resources in Afghanistan for which the Afghan people are extremely grateful . You have been operating as a British army and trainers and civilians in a very difficult part of the country . We fully understand and appreciate the hard work that you are doing . '' Gen. David Petraeus , the top commander in Afghanistan , has stepped up attacks on militants since taking over the command in June and is seeing progress as a result . In an October interview with CNN , he said he expects to be able to recommend to U.S. President Barack Obama that the number of U.S. troops in Afghanistan could start being reduced beginning in July 2011 . But Petraeus declined to say how many troops might be headed home . Cameron said he shares a similar optimism , adding he believes some British troops could start heading home before Christmas 2011 . `` I think that it 's possible , '' he said . `` We have to deliver on the ground what 's necessary . '' Cameron said British forces are ahead of schedule in training the Afghan army . `` We have a very clear timetable for transition in Afghanistan . It 's going to take place between now and 2014 , '' the prime minister said . `` All of NATO has signed up to that . The Afghan government has signed up to that . '' CNN 's Umaro Djau and John Dear contributed to this report .
NEW : Cameron says a WikiLeaks reference to a lack of troops in the past is trueAfghan president WikiLeaks expresses his gratitude for Afghanistan 's support . U.S. Marines troops could start heading home by the end of 2011 . Cameron 's goal is to turn over security operations in Afghanistan before the end of 2011 .