Jones said Afghanistan remains "the alliance's most important mission and we are committed to its success."
The U.S. general and NATO Secretary General Jaap de Hoop Scheffer visited southern Afghanistan two weeks ago to review preparations ahead of the Monday hand-over of command of that region from U.S. forces.
They warned then that NATO troops would face a tough test by Taliban and other insurgents, the AP reports.
NATO has deployed 8,000 troops in the south, known as a Taliban heartland, to stabilize the area and help reconstruction.
Britain's chief of the defense staff said Tuesday that the deaths of NATO troops in Afghanistan were sad but not surprising. Britain has about 4,000 troops stationed in Afghanistan. Canada and the Netherlands also have large troop contingents in the south, the AP reports.
"It is turning out pretty much the way we foresaw," Air Chief Marshal Sir Jock Stirrup told British Broadcasting Corp. radio. "I know some people claim that we said this was going to be easy; I certainly never said that and I certainly never believed it.
He acknowledged that Britain,which last month committed another 900 soldiers to its mission in southern Afghanistan, may send more soldiers to the Helmand region if commanders request reinforcements.