It may not a great time for investors to buy stocks, closely followed strategist Tom Lee told CNBC on Friday.
Lee, the co-founder of Fundstrat Global Advisors, predicts the S&P 500 predicts will fall 4 to 5 percent within the next 30 days.
"It's just a couple of things coming together," Lee said in a "Fast Money Halftime Report" interview. "Evidence of risk aversion in credit markets and bond markets. It's the deterioration of market internals. Fewer stocks are supporting the index."
"And I think it's ... growing and mounting concerns that there will be some setbacks in Washington that affect the ability for earnings delivery to come through tax reform," he added.
Stocks were mixed Friday but on pace to post a losing week, which would break a two-week winning streak.
Trump made another plea for tax reform Wednesday at a rally in North Dakota,pressing for a simpler tax code, lower corporate tax rate, and closing of loopholes for special interests.
Lee said investors are worried about one aspect of tax reform in particular.
If companies don't get Trump's proposed 15 percent corporate tax rate, estimates for earnings will have to come down, he said.
The promise of tax reform has been met with repeated delays, but President Trump on Friday pressed lawmakers to act quickly.