* Kerry makes unannounced visit to Afghanistan
* Deal covers U.S. troop presence in Afghanistan after 2014
* Karzai says deal can wait until after April vote
U.S. Secretary of State John Kerry met President Hamid Karzai in Afghanistan on Friday to try to advance negotiations over a security pact that have stalled over two issues that have become deal breakers for the Afghan government.
The United States says it wants the deal done by the end of October, while Karzai has declared it can wait until after presidential elections in April next year, further straining what has become a rocky relationship between the allies.
The deal will determine the presence of U.S. forces in Afghanistan after most are withdrawn in 2014 and a failure to reach an agreement could prompt Washington to pull out all of its forces at the end of 2014, an outcome known as the "zero option".
"The ball remains in the Afghans' court ... Time is of the essence, the longer it goes, the harder it is to plan," a State Department official said, speaking en route to Kabul.
The talks over the pact have stalled over two points.
One is a U.S. request to run independent counter-terrorism missions on Afghan territory, which have long infuriated Karzai. The Afghans instead want the United States to pass on information and let them handle the action.
The second sticking point is a U.S. refusal to guarantee protection from foreign forces as it could lead to offensive action against another ally, neighbouring Pakistan.
Shortly after arriving in Kabul, Kerry and his delegation were escorted to the presidential palace where he met Karzai. There were no visible tensions with Karzai inquiring about Kerry's recent visits to Indonesia, Brunei and Malaysia.
Kerry was joined by U.S. Ambassador to Afghanistan James Cunningham and Gen. Joseph Dunford, the top U.S. general to Afghanistan.
U.S. officials said Kerry did not intend to close a deal on the Bilateral Security Agreement (BSA) during the visit but would discuss "issues of mutual concern".
"This is really about us building momentum for the negotiators and helping establish conditions for success of the negotiations going forward," another State Department official told reporters.
The Washington Post reported on Thursday that the White House was increasingly willing to abandon plans for a long-term partnership with Afghanistan. While the Pentagon has pleaded for patience, the rest of the administration was fed up with Karzai and sees Afghanistan as a fading priority, the newspaper said.
"The Afghans' primary goal with the BSA is to come up with an agreement that meets their security needs, and we fully believe that what's on the table right now would do that," the official said.
The collapse of similar talks between the United States and Iraq in 2011 - triggered partly by Iraq's refusal to provide immunity to U.S. soldiers serving there - led to the United States pulling its troops out of the country.
Washington is concerned that as Afghan election campaigning intensifies it will be harder to broker a deal. Indeed, Karzai's brothers this week began their campaign take power and plan to offer the outgoing president, who is constitutionally barred from running again, a position in their government.
The election is considered the most crucial since the U.S.-led overthrow of the Taliban in 2001, which brought Karzai to power, and an opportunity to push the country away from years of damaging allegations of corruption and maladministration.
"It's going to be more difficult for them to focus on getting to a resolution of these issues, so we'd like to bring them to a close before we get to that point," the U.S. official added.