It's not clear yet whether strong Black Friday sales online will weaken growth on Cyber Monday, which has been the biggest e-commerce day in the United States in recent years.
"Cyber Monday will be a big day, but not as much of a big day as it has been in the past," said Mia Shernoff, executive vice president for Chase Paymentech, a payment-processing unit of J.P. Morgan Chase & Co.. "Faster broadband Internet connections in the office used to drive this. But now many consumers have faster connections at home and smart phones and tablets - they don't have to wait."
ComScore Chairman Gian Fulgoni said Cyber Monday online sales may reach $1.5 billion this year. That would be up 20 percent from the corresponding day last year - slower year-over-year growth than Thanksgiving and Black Friday.
More than 129 million Americans plan to shop online on Cyber Monday, up from almost 123 million on the same day last year, according to a survey conducted in recent days for the National Retail Federation.
The group also expects 85 percent of retailers to have a special promotion for Cyber Monday.
Amazon, the world's largest Internet retailer, will launch Cyber Monday deals at midnight on Sunday. The company is planning a limited time Cyber Monday promotion for its 7 inch Kindle Fire tablet, offering it at $129 instead of the regular $159, a spokesman said on Sunday.
MOBILE SHOPPING GROWTH
A big source of online shopping growth this holiday season has come from increased use of smart phones, which let people buy online even when they are in physical stores, and by tablet computers, which have spurred more online shopping in the evenings, Wingo and others said.
Mobile devices accounted for 26 percent of visits to retail websites and 16 percent of purchases on Black Friday. That was up from 18.1 percent and 10.3 percent, respectively, on the same day last year, according to International Business Machines , which analyzes online traffic and transactions from 500 U.S. retailers.
More than 20 million shoppers plan to use mobile devices on Cyber Monday, up from 17.8 million a year ago, the NRF said.