Ace economist Edward Yardeni predicts that the bull stock market will continue to charge regardless of whenever the Federal Reserve raises interest rates.

"Given that [a rate hike] has been so widely expected, the reaction should be minimal," the president of Yardeni Research told CNBC.

Yardeni described the global economy as being mired in "secular stagnation," which creates a positive environment for the equity and fixed-income markets.

"For the stock market and bond market, secular stagnation on a global basis means we have something in between," he told CNBC.

"We don't really have inflation, we don't really have deflation and central banks continue to maintain relatively easy money."

Investors also must not focus too much on global problems such as the crises in Greece and China.

"These have been worries all along in the bull market. The only serious problem we have with the market is valuation. Stocks are not cheap."

The S&P 500 has rallied nearly 27 percent in the past two years and is trading around 17 times forward earnings, CNBC reported.

Yardeni predicts the market will "continue to move higher."

"It's either going to be a one and done or a none and done," he said. "I see the S&P 500 ending this year at 2,150 and next year at 2,300."

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