Generals Abd al-Rashid Dostum and Atta Muhammad, whose forces clashed in October in the latest eruption of almost decade-long tensions, met Rumsfeld on Thursday at the headquarters of a British civilian-military reconstruction team.
The two men were both commanders in the anti-Taliban Northern Alliance which defeated the Taliban along with a US-led coalition in 2001.
A senior US official travelling with Rumsfeld said the visit was aimed at offering support to the Karzai government’s plan to stabilise the north.
The government wants to expand a UN-backed pilot programme to reintegrate demobilised fighters back into civilian life, in an effort to defuse tensions and dilute the power of warlords.
The official indicated, however, that neither Dostum nor Atta had signed an agreement to take part in the Disarmament, Demobilisation and Reintegration programme.
“We're going to be encouraging them to live up to the agreements to continue the reform programme that Karzai is pushing," he said.
Rumsfeld planned to travel later to meet Karzai and commanders of both the US-led coalition force and the NATO-run peacekeeping force, the International Security Assistance Force (ISAF).
Rumsfeld (R) will meet Afghan
rivals fighting for over a decade
Rumsfeld began his trip in Brussels at the weekend, where he suggested that US military operations in Afghanistan might eventually be put under a single NATO command.
Need to remain
Meanwhile, the head of the German troops serving in the ISAF has said the body will need to remain in Afghanistan for more than a decade before the country is truly stable.
ISAF "could remain for another 14 years while the country still has need for foreign assistance" and a new generation of Afghans reaches adulthood, said Colonel Rudolf Retzer in a newspaper interview.
Retzer, who heads the 1600-strong German contingent serving in the ISAF, said the current generation had known war for 24 years and could read and write only with difficulty.
In October the UN and NATO agreed to expand ISAF beyond Kabul to help clamp down on a recent rise in violence, blamed on a resurgent Taliban.
But so far the only concrete action has been that of German troops setting up a civil-military operation in the peaceful northern town of Kunduz.
Retzer was cautious about the prospects of quickly bringing peace and security to Afghanistan, where US-led forces toppled the Taliban regime at the end of 2001.