They will discuss a looming end of October deadline for completing a security deal to allow American troops to remain in Afghanistan after the end of the NATO-led military mission next year.
Kerry's unannounced visit to Kabul today comes as talks on the Bilateral Security Agreement have foundered over issues of Afghan sovereignty despite a year of negotiations.
The US wants a deal by the end of the month, but the discussions have stalled over Karzai's demand for American guarantees against future foreign intervention, a veiled reference to neighboring Pakistan.