The Federal Communications Commission had set the Monday deadline as an interim safeguard while providers of Internet calling, also known as "VoIP" for Voice over Internet Protocol, rush to comply with an FCC order requiring full emergency 911 capabilities by late November.
Vonage Holdings Corp., the biggest VoIP carrier with more than 800,000 subscribers, told The Associated Press Wednesday that 96 percent of its customer base have responded to the company's notices about 911 risks. But that still means as many as 31,000 accounts would need to be shut off as early as Tuesday.
Other leading carriers declined to quantify the response rate beyond the updates they were required to file with the FCC two weeks ago. AT&T Corp. spokesman Gary Morgenstern said customer acknowledgments are now "significantly higher" than the 77 percent figure it reported to the FCC on Aug. 10.
The FCC issued its order in May after a series of highly publicized incidents in which VoIP users were unable to connect with a live emergency dispatch operator when calling 911.
Vonage, AT&T and other carriers have indicated that they plan to comply with the FCC deadline to disconnect customers.
"There is no way to know just how close (to a 100 percent customer response) we will get by Monday," Vonage spokeswoman Brooke Schulz said.
She added that the company has been meeting with the FCC weekly "to seek their guidance as to how to implement the approaching Aug. 29 cutoff date."