U.S. Secretary of State John Kerry waves upon his arrival in Brussels, Belgium, Tuesday, Dec. 3, 2013. Kerry traveled to Belgium to attend the annual meeting of NATO foreign ministers in Brussels. AP Photo/Pablo Martinez Monsivais, Pool US Secretary of State John Kerry, right, is greeted on the tarmac by U.S. Ambassador to Belgium Denise Bauer, left, upon his arrival in Brussels, Belgium, Tuesday, Dec. 3, 2013. Kerry traveled to Belgium to attend the annual meeting of NATO foreign ministers. From left, Greek Foreign Minister Evangelos Venizelos, Belgian Foreign Minister Didier Reynders and Iceland's Foreign Minister Gunnar Bragi Sveinsson speak with each other during a meeting of the North Atlantic Council at NATO headquarters in Brussels on Tuesday, Dec. 3, 2013. U.S. Secretary of State John Kerry will join other NATO foreign ministers for a two-day meeting in hopes of persuading Afghan leaders to let international troops remain in the war-torn country beyond 2014. AP Photo/Virginia Mayo Italian Foreign Minister Emma Bonino, right, waits for the start of a meeting of the North Atlantic Council at NATO headquarters in Brussels on Tuesday, Dec. 3, 2013. From left, U.S. Secretary of State John Kerry, Slovenian Foreign Minister Karl Erjavec, NATO Secretary General Anders Fogh Rasmussen, Belgian Foreign Minister Didier Reynders and Spanish Foreign Minister Jose Manuel Garcia-Margallo greet each other during a meeting of the North Atlantic Council at NATO headquarters in Brussels on Tuesday, Dec. 3, 2013. BRUSSELS (AP) - Diplomats vexed over Afghanistan's future applied new pressure on the war-torn nation's leaders Tuesday to agree to allow thousands of foreign troops to remain there beyond next year, or risk being left with no international military force assistance. U.S. and NATO officials made in discussions in Brussels that they do not want to go to the so-called zero option in Afghanistan - even if doing so could free up thinning resources for other crises that may pose a greater threat to the world. But Afghan President Hamid Karzai's refusal - so far - to agree to a continued troop presence past 2014 puts the U.S. and its strongest traditional allies in the awkward political position of threatening to leave even as they make the case to stay. If Karzai continues to block an agreement, "there can be no deployment and the planned assistance will be put at risk," NATO Secretary General Anders Fogh Rasmussen said Tuesday before the start of an annual meeting of diplomats and security officials. "It is my firm hope and intention therefore to continue our efforts to support Afghanistan, once these agreements are concluded," Rasmussen said. He stopped short of demanding a deadline for Afghanistan's president to sign a bilateral security pact with the United States. NATO has said such a pact is needed to move forward with its own plans to help the country after the combat mission ends in 2014 and local forces take full control of security. American officials, led by national security adviser Susan Rice, have demanded that Karzai sign a security agreement with the U.S. by the end of the year. Failure to do so, the officials have said, would leave Washington with little choice but to prepare for a full troop withdrawal. U.S. officials have said that the U.S. and NATO could keep between 8,000 and 12,000 troops there. Of those, the U.S. is expected to provide no more than 8,000 to train, equip and assist Afghan security forces. If Karzai rejects the U.S. agreement, any alternate pact with NATO will almost certainly fall through as well, officials said. Karzai has tentatively endorsed the deal, but refuses to sign it. He has said it is a decision that should be left to his successor after Afghan presidential elections next April. Additionally, Karzai wants all airstrikes and foreign raids on Afghan homes to stop if the United States expects him to sign it. He upbraided the U.S. for a drone strike that killed a child last week. Civilian deaths at the hands of U.S. and allied soldiers have been a key source of contention in increasingly tense relations with Karzai over the years. NATO officials, including U.S. Secretary of State John Kerry, will meet Wednesday with acting Afghan Foreign Minister Zarar Ahmad and Interior Minister Mohammad Daudzai to press an agreement. Although Karzai is balking at the pact, other senior Afghan officials have signaled their support for continued assistance from foreign forces, and a council of tribal elders known as the Loya Jirga last month urged that it be signed by the end of this month. A senior U.S. official said Washington and NATO strongly want to continue training and advising Afghan security forces. "But the Afghans have to make it clear that we are welcome and that there will be clear rules of the road," said the official, who was not authorized to discuss the issue by name and briefed reporters on condition of anonymity. On Twitter: Lara Jakes at https://twitter.com/larajakesAP and Jamey Keaten at https://twitter.com/jameykeaten