LOS CABOS, MEXICO - President Obama took a shot at the Romney campaign Tuesday for leveling criticism at him overseas, in violation of the American tradition of politics stopping at the water's edge, an adage coined in 1947 by Sen. Arthur Vandenberg, R-Mich.

The president, at the conclusion of the G20 international summit, took questions from three reporters, one of whom asked about an op-ed earlier this month in the German business journal Handelsblatt written by R. Glenn Hubbard, dean of the Columbia Business School and an economic adviser to Republican presidential candidate Mitt Romney. Hubbard wrote that "President Obama's advice to the Germans and Europe has…the same flaws as his own economic policy - that it pays for itself over the long term if we focus on short-term business promotion."

"These recommendations are not only unwise," Hubbard wrote, "they also reveal ignorance of the causes of the crisis and of a growth trend in the future," Hubbard writes. "Long-term confidence in solid government financing shores up growth and enables the same scope for short-term transitional assistance. Mitt Romney, Obama's Republican opponent, understands this very well and advises a gradual fiscal consolidation for the U.S.: structural reform to stimulate growth."

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President Obama begged off addressing the criticism, saying "with respect to Mr. Romney's advisers, I'd suggest you go talk to Mr. Romney about his advisers. I would point out that we have one president at a time and one administration at a time. And I think traditionally, the notion has been that America's political differences end at the water's edge."

The president also suggested that Hubbard "may not be familiar with what our suggestions to the Germans have been. I think sometimes back home, there's a desire to superimpose whatever ideological arguments are taking place back home onto a very complicated situation in Europe."

The European economic mess has been a focus at this summit, even though only four G-20 members - France, Germany, Italy and the European Union - are present. There seemed to be some consensus here that the European countries focus on job growth and infrastructure and avoid concentrating only on austerity and reducing deficits.

-Jake Tapper and Mary Bruce