Job openings in the U.S. increased in February and hiring climbed to the highest level in more than three years, signaling employers are optimistic about the economic outlook.

The number of positions waiting to be filled totaled 3.5 million in February, up from a revised 3.48 million the prior month that was higher than previously estimated, the Labor Department said today in a statement posted on its website. More people were taken on than at any time since October 2008, while the pace of firings was little changed, the report showed.

Better employment prospects may attract more people into the labor market and help restore some of the 5 million jobs yet to be recovered after the 18-month economic slump ended in June 2009. The pickup in hiring may ease concerns raised by Federal Reserve Chairman Ben S. Bernanke that much of the improvement in the job market stems from fewer firings instead of more hiring.

“All of the broader fundamentals point to a stronger labor market,” Eric Green, chief market economist at TD Securities Inc. in New York, said before the report. At the same time, he said, “job growth is running well ahead of domestic demand. You will not be able to maintain this pace of job growth unless you have some promise that demand will be picking up.”