Karzai: "Disciplined, well-equipped and neutral army"
Defence Minister Mohammad Fahim said the new army would avoid the mistakes of the past and keep out of politics.
He was speaking as the warlords, from all over Afghanistan, reportedly vowed to work together in building the army.
The interim leader, Hamid Karzai, said it was the greatest show of unity among Afghanistan's ethnic leaders in 23 years.
"You have come here to strengthen stability and protect Afghanistan's national interests," he told the warlords at the start of their two-day meeting in Kabul.
Mr Karzai echoed his defence minister in calling for a "disciplined and well-equipped army which stays neutral on political issues".
"I promise that there will not be chaos and war in this country again," the defence minister said.
"We want all people in Afghanistan from any tribe to be Afghans and think about their national interests first."
Former foes
Most of Afghanistan's major warlords were present, including the controversial governor of Herat, Ismail Khan, and ethnic Uzbek leader General Dostum.
"Enough of fighting," General Dostum told the gathering.
"What is the use? Let's break out of this vicious circle. Whether from north, south, east or west, we are all brothers. I am willing to give my blood for this army."
One of the general's rivals, General Atta, for his part condemned "tribalism" and urged democracy.
The conference is due to discuss the size and ethnic make-up of the army.
Foreign peacekeepers are already training 600 soldiers for the new army in Kabul.
Reporters noted that while all of the country's main factions were represented, the conference was dominated by outsize pictures of the assassinated Northern Alliance leader, Ahmad Shah Masood.