Amazon.com posted quarterly results Thursday that fell short of expectations and handed in a weak revenue outlook.



Additionally, Amazon said during its conference call it may increase the cost of its popular Amazon Prime subscription by $20 to $40 due to higher fuel and other shipping costs.



There were no immediate details on when or how Amazon would make the decision during the call. The company did not disclose the exact number of Prime customers.

"We have added massive selection and digital content to the service—Kindle owners lending library, Prime instant video," according to CFO Thomas Szkutak during the call. "It's great value for customers. We see customers love it and we will continue to make that better over time."

In December, Amazon said that its Prime service had a "record-setting holiday season." According to the company, more than 1 million people signed up in the third week of December alone. Prime members get free two-day shipping on eligible items, free streaming of 150,000-plus movies and TV episodes, and free e-book borrowing from a library of more than 475,000 titles.