Art Cashin says the rally for Nasdaq stocks "has been marked by almost negative breadth" and unimpressive trading volume.
Cashin, UBS' director of floor operations at the NYSE, told CNBC's Bob Pisani around midday that has "raised the antenna on suspicions that (we may be) starting to flag."
"We've had one heck of a run here in all the averages, but are going to begin to run out of new fuel? We'll see. Maybe with rates at the level they are, it won't happen."