He has in the past made inflammatory remarks only to then change his mind.
He signed a strategic partnership with President Obama last year despite criticizing the United States for its military actions in Afghanistan, including night raids against Afghan homes and air strikes that resulted in civilian casualties.
Karzai's reticence to sign could also be attributed to his awareness that previous leaders of his country historically have been punished if seen as selling out to foreign interests.
Karzai told the delegates to the Loya Jirga that his decision had to do with the lack of trust between him and the United States.