Citi's top global economist expects overheating: 'This will be a mess'

5 stages of Trump trade

As the markets continue cheering Donald Trump's promised mix of tax reform and infrastructure spending, Citi's chief global economist sees a less-than-rosy picture a couple of years out.

While Willem Buiter said the U.S. does not need fiscal stimulus, he thinks corporate and personal tax reforms and infrastructure spending would all be positives.

"Couple years from now this will be overheating, and this will be a mess, but markets never see ahead more than two years," he said Friday on "Squawk on the Street."

Currently, Buiter views the market as "slightly overegged" but says he remains "optimistically cautious."

While Alan Ruskin, global head of Group-of-10 foreign exchange strategy at Deutsche Bank, also does not think stimulus is called for, he does think reform is.

Ruskin, appearing on "Squawk on the Street," called the border adjustment tax "the big story," saying "the markets will respond enormously to it." Such a tax would be designed to discourage imports to the U.S. and encourage exports.

"If we get a border adjustment tax, the dollar, I think, is really going to fly," he added.