Afghan elders at a tribal assembly in Kabul on Sunday called for a security deal with the United States to be signed this year.
The pact would allow up to 15,000 US troops to remain in Afghanistan when combat operations end in 2014.
But President Hamid Karzai wants to delay the deal. Opening the assembly on Thursday, Mr Karzai said he wanted to delay signing a Bilateral Security Agreement until after the presidential election in April.
Another condition he stipulated was US co-operation in efforts to make peace with the Taliban.
But the loya jirga gathering of about 2500 chieftains, tribal elders and politicians overwhelmingly backed the pact on Sunday and urged Mr Karzai to sign it by the end of this year.
"Given the current situation in, and Afghanistan's need ... the contents of this agreement as a whole is endorsed by the members of this Loya Jirga," the declaration said.
"The Loya Jirga requests the president to sign the agreement before the end of 2013."
The BBC reports the agreement still has to be approved by the Afghan parliament also.
The bulk of NATO's 75,000 remaining troops will pull out next year after 12 years of war against the Taliban.
