(CNN) -- A major missing piece threatens to hold up a security deal between Afghanistan and the United States: President Hamid Karzai's signature.
The Afghan President told U.S. National Security Adviser Susan Rice Monday that he isn't ready to approve the Bilateral Security Agreement yet and "outlined new conditions for signing the agreement," according to a statement released by the White House.
Rice told Karzai that delaying the deal -- which would allow for the presence of a limited number of U.S. troops beyond next year -- until after Afghanistan's 2014 elections "is not viable," the White House said.
"It would not provide the United States and NATO allies the clarity necessary to plan for a potential post-2014 military presence," the statement said. "Nor would it provide Afghans with the certainty they deserve regarding their future, in the critical months preceding elections."
So what happens if Karzai doesn't sign it soon? U.S. and NATO troops could pull out of Afghanistan earlier than expected.
"The U.S. would have no choice but to initiate planning for a post-2014 future in which there would be no U.S. or NATO troop presence in Afghanistan," the White House said.
On Sunday a vast majority of 2,500 Afghan elders voted to recommend the joint security agreement with the United States and urged Karzai to sign it before the end of the year.
Karzai had said he would follow their recommendation under one condition -- that U.S. forces do not conduct house raids.
"If U.S. military forces conduct military operations on Afghan homes even one more time, then there will be no BSA and we won't sign it," Karzai said on Sunday. "They should give assurance about this to us before I sign it."
But then he moved the goal posts, refusing to sign until after the presidential election next spring.
His last-minute decision to delay signing the pact was both classic Karzai -- a tricky negotiator to the last -- and a breakaway move that provides political cover for any U.S. officials who prefer the so-called zero option of leaving no U.S. troops in Afghanistan.
It's a decision that could also have political implications for Karzai in Afghanistan, shoring up his anti-American credentials ahead of next year's presidential election.
Karzai himself cannot stand again for president under the current constitution, but he remains highly influential in Afghan politics, whose entire cast he has helped shape since the U.S. invasion in 2001.
Abdullah Abdullah, who ran against Karzai in 2009 before dropping out of the race amid allegations of election fraud, told CNN's "Amanpour" on Monday that political motivations are clouding Karzai's approach.
"These negotiations between Afghanistan and the United States are being delayed not because of the content of the Bilateral Security Agreement," Abdullah said, "but primarily because of the personal feelings or personal interests of President Karzai."
CNN's Nick Paton Walsh, Christiane Amanpour and Masoud Popolzai contributed to this report.