While the S&P 500 and Dow Jones Industrial Average stand within 2 percent of their record highs, there is growing danger of a strong market correction, says Dennis Gartman, publisher of The Gartman Letter.

He's concerned about weakness in the Russell 2000 and Nasdaq Composite indexes. "As the Dow continues to make new highs, yet the Russell, the Nasdaq seem to be showing signs of weakness, it is a little disconcerting to me," he told CNBC.

"With each passing day, we are more and more fearful too that a correction of some very real magnitude is hard upon us," Gartman wrote in the Letter Monday, which was obtained by CNBC.

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The Russell 2000 index of small-cap stocks has dropped 9.2 percent from its March 4 record high, while the technology-laden Nasdaq Composite has fallen 5.9 percent from its 13-year peak March 6.

The divergence between the Dow and other indices now reminds Gartman of the early 1970s, when the "Nifty Fifty" and the Dow thrived, while the overall market stumbled.

Still, the five-year-old bull market remains intact, Gartman said. "The most bearish one can be here, is neutral."

Concern about corporate profits is weighing on some investors.

"What we're seeing is a re-assessment of the growth prospects of earnings," Brad McMillan, chief investment officer for Commonwealth Financial Network, told Bloomberg. "It's not a question of are we going to grow, because we are. It's are we going to grow as fast as we thought we would?"

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