Microsoft on Tuesday said workers who responded to an online Office survey reported two days out of the workweek were a waste of time, with U.S. workers blaming procrastination as the top cause.

According to the survey of nearly 40,000 people in 200 countries, workers clock an average of 45 hours per week, but consider about 17 hours of that unproductive. U.S. workers, however, believe only 16 hours are wasted.

In the U.S, the biggest productivity pitfalls were procrastination -- picked by 42 percent of those polled -- lack of team communication (39 percent), and ineffective meetings (34 percent). Global numbers were quite different. There, procrastination got 29 percent of the vote, while unclear objectives and ineffective meetings garnered 32 percent.

More than a third of the hours down the tubes are those wasted in meetings, said American respondents, who estimated that they spent 5.5 hours in meetings per week, with 71 percent of those workers feeling meetings are unproductive.

E-mail, boon to some, bane to others, was also blamed. Globally, workers said they receive an average of 42 e-mail messages each day. The number pops to 56 messages daily for U.S. workers.

Microsoft ran the poll to tout productivity software. Among the findings: 55 percent of the people surveyed said they relate their productivity directly to their software; in the U.S., that number jumped to 61 percent.

"With so many people saying they aren't as productive as they could be and that they rely on technology to achieve their productivity goals, Microsoft has a great opportunity to provide the tools to help them quickly and effectively meet their needs," said Chris Capossela, vice president for Microsoft's information worker product group (which includes Office).