By David Loyn
BBC News, Kabul
Nato Secretary General Jaap de Hoop Scheffer has completed a two-day visit to Afghanistan at a time of unprecedented tensions in the alliance over its first major operation outside its area in Europe and the North Atlantic.
President Hamid Karzai told the secretary general that he would attend the crucial summit at Bucharest in April, when the issue of Canada's threat to pull out its troops unless more nations send forces into the south will be discussed.
Nato's head says more needs to be done to train Afghan troops
The US has put in 3,200 more troops for now, bringing the number of foreign soldiers in the country above 50,000.
But these reinforcements are only available for six months and no other countries have yet come forward to fill the gap.
A warning by US Secretary of Defence Robert Gates of a "two-speed" alliance has raised the political stakes ahead of the summit.
President Karzai sees the war over the Taliban as "won", describing what remains as a terrorist problem.
He told a press conference that he would welcome whatever participation Nato countries can provide.
"What we want is at the end of the day, a partnership in Afghanistan that each one of us is happy about."
There has been an upsurge in suicide attacks recently, including three in Kandahar in as many days this week.
But despite the continuing insecurity more than six years after the defeat of the Taliban government, President Karzai denied that the international community had failed, pointing to advances in health care and education and improvements in roads that have connected outlying districts.
Mr de Hoop Scheffer said that those still fighting against the government and foreign forces are "spoilers", who are "hijacking a beautiful religion that is Islam".
Canada wants more Nato backing for its troops in Afghanistan
In order to combat the problem he said that there needed to be commitment in Afghanistan for the long term.
But he faced the problem of short-term political horizons in Europe. "The international community has lost the translation of the word patience," he said.
'Afghan face needed'
During his visit he saw progress in Musa Qala, the town in Helmand in the south that was taken from the Taliban in December.
He said that the Afghan National Army was working well alongside British forces in the area.
Mr de Hoop Scheffer said it was essential that both the security challenges, and the reconstruction effort took on more of an Afghan face, and had Afghan ownership.
He admitted that the challenges were tough, and that Nato had not done enough yet in training Afghan forces.
Troops from Germany, a nation that will not put troops into the more dangerous combat areas, are doing more of the training.
More countries are now allowing involvement of their forces in the combat zone in the south.
A year ago there were eight countries engaged there. By the time of the Nato summit in Bucharest there will be 15.
But most of these are offering only dozens of troops not the thousands that Canada says are needed to provide backing for its mission.
Mr de Hoop Scheffer said Nato's involvement in Afghanistan was "not one of choice but of necessity".