President Hamid Karzai said this week that he was prepared to walk away from the Bilateral Security Agreement (BSA) talks if Afghanistan was not happy with its conditions.
But the United States has repeatedly pressed for the pact to be signed by the end of this month so that the US-led NATO military coalition can schedule its withdrawal of 87,000 combat troops by December 2014.
"President Obama and President Karzai reaffirmed both back in January that the goal here was to complete the BSA in October," a state department official travelling with Kerry told reporters.
"Uncertainty about an incomplete BSA could erode the resolve among NATO allies, makes (it) more difficult to plan for the US, makes (it) more difficult to plan for our NATO allies. The goal has not changed and that is what we continue to press for."
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Karzai said he refused to be rushed into signing the deal and would first seek approval from a traditional grand assembly to be convened in about month's time.
"If it doesn't suit us and if it doesn't suit them, then naturally we will go separate ways," Karzai said in a BBC interview in Kabul broadcast on Monday.
According to the Afghan government, talks ground to a halt over US demands for the right to conduct unilateral military operations, and on how the US would pledge to protect Afghanistan.
The collapse of a similar agreement with Iraq in 2011 led to the US pulling troops out of the country, which is currently suffering its worst sectarian violence since 2008.
But Kabul has dismissed the possibility that the US may enact the "zero option" of a complete pull-out after its troops have fought the Taliban for 13 years since the 9/11 attacks in 2001.
"We will be discussing where we are and see to continue to make progress. Negotiations were ongoing before we arrived and will be ongoing after we depart from Kabul. So that is not the expectation in terms of conclusion."
Karzai officially suspended BSA talks in June in a furious reaction to the Taliban opening a liaison office in Qatar that was presented as an embassy for a government in waiting.