WASHINGTON -- Sen. John McCain (R-Ariz.) is standing by a recent Mitt Romney ad attacking President Barack Obama on the economy, even though it mirrors a spot the Obama campaign aired against McCain in 2008 that the senator criticized at the time.

The 2008 Obama ad quoted McCain, at the time the GOP presidential nominee, saying, "The fundamentals of our economy are strong." At the end, it asked: "How can John McCain fix our economy if he doesn't understand it's broken?"

The Romney ad quotes Obama saying "the private sector is doing fine." It ends with: "How can President Obama fix our economy if he doesn't understand it's broken?"

The two ads even use the same music.

In 2008, McCain attempted to clarify that he had been referring to entrepreneurship and innovation as the fundamentals of the economy that remained strong.

Obama, too, quickly clarified his remarks about the private sector, saying it was "absolutely clear" the economy was not fine.

On NBC's "Meet the Press" on Sunday, host David Gregory asked McCain about the ads' similarities, and whether he believed that it was unfair of Romney to run the ad against Obama.

"I would imagine you would say to Mitt Romney, 'That's an unfair knock against President Obama,' just as you thought it was an unfair knock against you," said Gregory.

"Of course not," replied McCain. "At the time, the stock market had just fallen 700 points. Americans were frightened. I wanted to reassure the American people that the fundamentals of our economy were strong. It's still the best system in the world."