Afghan President Hamid Karzai said the US needs to bring peace to Afghanistan before he will sign a security deal enabling Washington to keep troops in the country beyond next year.
Karzai rejected calls by Afghanistan's council of tribal elders - the Loya Jirga - to sign the security deal.
He told the assembly: "If there is no peace, then this agreement will bring misfortune to Afghanistan.
"Peace is our precondition. America should bring us peace and then we will sign it."
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The operation to recover the unexploded bomb near the Houses of Parliament let to disruption in central London overnight.
Southern parts of England and Wales will see sunny skies after a frosty start.
A police spokesman said the incident in the Bourke Street Mall on Friday was not related to terrorism.