"It is easy to see that we become an issue in the campaign, and not in a way that serves the U.S. interests," Markey said. "There could be a competition to show who is least willing to kowtow to the Americans. And then when they negotiate in that way, you never get a BSA. Then you have an Iraq situation, where we have to leave. But for Afghanistan, it's more dangerous. It's even more unstable and the regional consequences are of greater concern to India, Pakistan and even China."

Moreover, the lack of a deal would impact NATO's military planning. The United States wants to give its troops, and those of other countries, enough time to prepare for keeping troops in Afghanistan. Other NATO countries, including Germany, say they will be unable to remain in Afghanistan if the United States and Afghanistan do not reach a deal. A total withdrawal would also put at risk billions of dollars in international aid.

"As a practical matter it will be difficult for us and our NATO partners to deliver on pledges we have made regarding both security and economic programs," one senior administration official said.