Afghanistan and the United States have finalised details of a crucial security pact just two days before it was due to be voted on by Afghan tribal and political leaders, an Afghan official said Tuesday. Aimal Faizi, spokesman for President Hamid Karzai, told reporters in Kabul that the deal would allow US troops to enter Afghan homes but only in "extraordinary circumstances" where there was an urgent risk to life, ending a sticking point which had threatened to derail the agreement.