Carter is scheduled to confer with Afghan President Ashraf Ghani and other leaders as well as top US officers and diplomats.
Under the current plan, the 10,000-strong US force is due to drop to roughly 5,000 by the end of 2015 and then pull out altogether by the time Barack Obama leaves office in two years` time.
But the Obama administration has already adjusted the pace of the withdrawal, allowing 1,000 additional American forces to remain this year.
Afghan leaders and some lawmakers have urged President Obama to reconsider the withdrawal timetable, warning that an early US exit could jeopardize security and discourage international aid.
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