President Obama, speaking at the close of the G-20 summit in Mexico, scolded one of Mitt Romney's advisers for authoring a critique in a German publication of the president's economic prescription for Europe.

"I would point out that we have one president at a time and one administration at a time," Obama said. "And I think traditionally the notion has been that America's political differences end at the water's edge."

Obama, at a press conference Tuesday, was asked about the op-ed written by Romney adviser R. Glenn Hubbard and published in the German business publication Handelsblatt earlier this month.

The op-ed, titled "Do Not Learn From America," criticized Obama for trying, Hubbard wrote, to convince Germany to prop up weaker nations in the eurozone.

"These recommendations are not only unwise, they also reveal ignorance of the causes of the crisis and of a growth trend in the future," he wrote, according to a translation from The New York Times.