From the Washington Post:

One official, who like others spoke on the condition of anonymity due to the issue’s sensitivity, said Tuesday that the U.S. military now assesses a collapse could occur within 90 days. Others said it could happen within a month. Some officials said that although they were not authorized to discuss the assessment, they see the situation in Afghanistan as more dire than it was in June, when intelligence officials assessed a fall could come as soon as six months after the withdrawal of the U.S. military.