Investors should resist the temptation to sell the rally in stock markets, UBS strategist Jeremy Zirin said Thursday.
The and Dow Jones industrial average have recently touched new highs, and both indexes are up more than 6 percent this year. That rally is underpinned by solid fundamentals, according to Zirin, chief equity strategist at UBS Wealth Management Research.
"Essentially, that data has just improved. So post-Brexit, what's happened? We've seen the labor market report improve, we've seen the ISM surveys, both manufacturing and nonmanufacturing improve. We've seen consumer spending perk up," he told CNBC's "Squawk Box."
And while earnings this season thus far point to "flattish" growth, that is much better than the 6 percent decline in the first quarter, he said.
Asked what happens when analysts raise the bar for earnings, Zirin said valuations are "reasonably good" and "well supported." So long as economic data continue to improve, the bar will not be raised too high, he added.
Earnings are poised to turn positive after a four-quarter profit recession caused in large part by a protracted oil price rout that badly bruised the energy sector and a U.S. dollar rally that hobbled multinationals, he said.
Improving economic data and healthier markets would likely put the Federal Reserve back on track to raise interest rates, following a pause in the wake of Britain's vote to leave the European Union and dismal May U.S. jobs data, which was offset by a blockbuster June report.
But Zirin said he'd be much more concerned if the Fed remains on hold.
"We want to see some economic normalization, which leads to policy normalization," he said.
Brian Rogers, chairman and chief investment officer at T. Rowe Price, told CNBC the market has proven resilient in the face of the Brexit vote, and U.S. economic news has been good.
The market, however, has been treading water because growth has been scarce and earnings expansion remains under pressure, he said. Still, stock valuations are not too extended, he added.
"We're in this period of really building a base, I suppose, and waiting for the economy to pick up at some point," he told "Squawk Box."