Tony Blair vowed yesterday there must be no return to the "sickness and evil" of the Taliban regime in Afghanistan which led to the horrors of the 9/11 terror attacks.
Standing alongside President Hamid Karzai in the grounds of the presidential palace in Kabul, Mr Blair insisted that the international community had no choice but to continue the fight against the insurgency.
"What is the alternative? We came to Afghanistan because the sickness and evil that was in Afghanistan came to us," he told a joint news conference.
Earlier Mr Blair flew into Camp Bastion, the main British base in Helmand Province, for a morale-boosting visit to meet the troops who have borne the brunt of much of the fighting in recent months.
Standing on a raised platform surrounded by soldiers in the desolate desert landscape, the Prime Minister paid tribute to their courage and dedication.
He told them it was vital the country was not allowed to fall back into the hands of al-Qaida and the Taliban.
"Here in this extraordinary piece of desert is where the future of the world's security in the early 21st century will be played out," he told them.
"We know that the only way to secure peace sometimes is to be prepared to fight for it."
Later, in Kabul, Mr Blair met General David Richards, the British officer commanding the 31,500-strong Nato international security and assistance force.
Despite the fierce fighting of the summer – particularly in Helmand – Gen Richards insisted the international forces were gaining ground against the Taliban.
He said: "Since the summer there has been a huge reduction in the number of incidents. There is a different atmosphere. I genuinely believe this is winnable."
President Karzai also struck a positive note, pointing to the improvements in the economy and health care since the fall of the Taliban government five years ago.
"The international community will surely stay with us until Afghanistan is firmly on its feet. Once Afghanistan is firmly on its feet, no evil force can return to Afghanistan," he said.
Yesterday's visit comes ahead of next week's Nato summit in Riga where Britain and the US are expected to press other alliance members to commit troops to southern Afghanistan, where the worst of the fighting has taken place.
Speaking at his Press conference with President Karzai, the Prime Minister said: "We came to Afghanistan because it was obvious that the problem in Afghanistan had become a problem for the world.
"We have got to stay committed for as long as it takes for our own security, not just for the sake of the Afghan people."
He added: "The alternative is that we go back to an Afghanistan that was not just misery for its people but ended up with violence and death being exported around the world.
"That's not an alternative any of us should contemplate."
Mr Blair warned victory required a long-term effort.
"These situations often are a long time in the creating and they need to be a long time in the resolving," he said.
Nato leaders meet for a summit later this month in the Latvian capital Riga.
"Now is the right time... to bring into focus the need for us to stay with the Afghans in their journey of progress and to rediscover within ourselves the vision that took us here and should keep us here until the job is done," he said.
Combating the roots of the Taliban was a "generation-long struggle", he warned.
"I'm not saying that we remain here in the same way for that length of time.
"The roots of the Taliban, al-Qaida, this type of
global terrorism, are deep and where they gained a foothold in a country like Afghanistan it is going to take time to banish that for good. But I think there is sufficient sign of progress here that it should give us some hope for the future."