The U.S. economy is strong even though third-quarter GDP will not be stellar, RBS' Michelle Girard said Monday.
Economists expect third-quarter GDP — due Thursday — to come in at 1.4 percent, well below the final second-quarter reading of 3.9 percent, according to a Dow Jones estimate.
"I think the U.S. economy is stronger than the credit it's getting," Girard, RBS' chief U.S. economist, told CNBC's "Squawk Box." "The private domestic economy — if you look at consumer and business spending and housing — has been growing better than 3 percent."
"Thursday's GDP number is not going to look good on the surface, but if you look at consumer spending and housing and business spending, the numbers are going to be closer to 4 percent."
Last week, the Commerce Department said U.S. housing starts rose 6.5 percent month over month. Existing home sales rose more than expected in September to the second-highest monthly sales pace since February 2007.
Still, not everyone agrees with Girard's assessment.
Mike Thompson, managing director at S&P Investment Advisory Services, told "Squawk Box" that the weakness in the U.S. economy is reflected on corporate earnings.
"They can't break out on [revenue]. [Earnings are] being maintained through a lot of cost cutting and efficiency gathering," he said. "It's a phenomenon that hasn't been seen in kind of a very long time. Companies seem to be hitting a wall."
Still, the three major indexes managed to post weekly gains last week.
"Whatever positive news we're getting now from the market is largely going to be borrowing from 2016 unless we start to get better earnings and revenues," Jason Trennert, chief investment officer at Strategas Research Partners, told "Squawk Box."
"This is mainly because the Fed has lost credibility and I think most people have come to the realization that the Fed's ability to influence the economy is weak," he said.
The Federal Reserve is scheduled to begin its two-day October monetary policy meeting Tuesday.
—Reuters contributed to this report.