Arizona Republican John McCain and several other U.S. senators say they've warned the Afghan president that a failure to sign a key Afghan-U.S. security deal would pose a threat to the country and the region.
Hamid Karzai has delayed signing the accord with the United States, which would for allow American troops to remain in Afghanistan beyond the exit date for the NATO mission at the end of this year.
McCain said after a meeting Thursday with Karzai that he's "confident the differences have been narrowed to the point that we can resolve them" in a few days or weeks.
Republicans John Barrasso of Wyoming and Lindsey Graham of South Carolina also met with Karzai.
Without a signed deal, all U.S. and NATO forces would have to withdraw from Afghanistan.