Amazon.com

(AMZN) - Get Report

was up 6.3% in midmorning after CEO Jeff Bezos said on

CNBC

that he stands by his promise that the online retailer will achieve a pro forma operating profit by the end of the year.

Bezos said "it's not a guarantee but it's something we're working very hard on" and defended the pro forma figures as a legitimate measure of the company's health.