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 don'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.