The deadlock over the fraud-tainted election has left Afghanistan in paralysis as two rival candidates are locked in a battle to succeed outgoing President Hamid Karzai, who has declined to attend the NATO gathering.
NATO's combat mission against the Taliban insurgents ends this year and the summit, starting in Britain on Thursday, is set to decide on a follow-up support mission widely seen as crucial to maintaining fragile nationwide stability.
"We are preparing to send the minister of defence to the NATO summit to represent the Afghan government," Karzai's spokesman Aimal Faizi said.
"If the president-elect is declared just before the summit and we do not have time for the inauguration, then the president-elect will be given an authorisation letter by the current president to attend."
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The summit is meant to confirm NATO's continued funding for the Afghan army and police, who are struggling to hold back the Taliban with declining assistance from US-led forces.
Rival presidential candidates Ashraf Ghani and Abdullah Abdullah both claim victory in the June 14 election, which has been engulfed in allegations of fraud.
The latest inauguration deadline of September 2 was abandoned as a UN-supervised audit of all eight million votes has fallen behind schedule.