Richard Weiss, senior portfolio manager at American Century Investments, tells CNBC's "Power Lunch" on Wednesday there are issues weighing on the market, including uncertainty about the Fed and China.
"Ripples and reverberations could pull Europe and even U.S. south given how weak Euroland growth is," Weiss said.
He is also concerned about political uncertainty and conflict in the Middle East.
"Combine that with unattractive U.S. equity market valuations and the prospect of higher interest rates and you have a potentially toxic combination," Weiss said.
He believes the best strategy now is to remain a little defensive and not buy blindly on the market dips.
The Dow and S&P 500 are lower during trading, while the Nasdaq is slightly higher.