Kerry, whose visit to Kabul was unannounced, was to meet with President Hamid Karzai to try to resolve the two remaining obstacles in talks on a long-term security pact that would allow U.S. forces to remain in Afghanistan after the NATO combat mission ends in 2014, The New York Times reported.
Because both sides seemed entrenched, a senior Western diplomat put the odds of reaching an accord at "no better than 50-50."
The two sides face trying to resolve a pair of demands Karzai says must be met but the Obama administration said it can't or won't consider.
The first demand is that the United States guarantee Afghanistan's security just as it would if would if the country were a NATO ally, which could compel the United States to send troops on raids into Pakistan, an ally of Washington and a nuclear-armed power, the Times said.
Karzai also won't allow U.S. forces to keep hunting for al-Qaida operatives in his country, wanting instead for the United States to turn over any intelligence it gathers to Afghan forces, who then would conduct the raids, the Times said.
If the Americans are unwilling to meet the conditions, "they can leave," Karzai told the BBC earlier this week.
The Obama administration set an Oct. 31 deadline for striking a deal to keep troops in Afghanistan. While administration officials said the deadline isn't firm, they also say the White House wants a deal worked out in principle soon or it will walk away from the talks and begin preparing for a pullout similar to Iraq after talks failed to reach an agreement on a U.S. military presence remaining after a formal withdrawal of combat forces.
After meeting with Karzai, Kerry will travel on Saturday to Paris and London.
Before his trip to Afghanistan, Kerry opened the fourth Global Entrepreneurship Summit in Kuala Lumpur, Malaysia. The summit was founded by U.S. President Obama as a way to help promote entrepreneurship around the world.
"Supporting your creativity and persistence is a key component of our foreign policy agenda -- which today, more than ever before, is about economic policy, too," Kerry said in his opening remarks.