U.S. Defense Secretary Jim Mattis says it's too early to tell if any of the overtures between North and South Korea during the Olympic Games are creating a chance for peace on the Korean Peninsula.

But he rejected any suggestion Sunday that even a temporary warming of relations between the North and South could drive a wedge between Seoul and Washington.

His remarks came after North Korean dictator Kim Jong Un's sister, who is attending the Olympics, invited South Korea's president, Moon Jae-in, to visit Pyongyang.

Moon has not yet accepted the invitation from Kim Yo Jong, although he has said before he'd be willing to visit if it would help end the North's pursuit of nuclear weapons and its decades of hostility and threats against the South.

Mattis said it's unclear "if using the Olympics in a way to reduce tension — if that's going to have any traction once the Olympics are over. We can't say right now."

Speaking to reporters traveling with him on a weeklong trip to Europe, Mattis said the North's decision to hold a recent military parade that highlighted its ballistic missiles confuses any messages of thawing tensions on the peninsula.

"I don't know if it's a sign," Mattis said. "That's a very strange time if, in fact, he's trying to show a warming to the country that he has attacked repeatedly as an American puppet."

He said that when he met South Korea's defense minister in January, it was made clear "there is no wedge that can be driven between us by North Korea."

Mattis is scheduled to meet in Rome with about a dozen defense ministers who are involved in the coalition fighting the Islamic State group in Iraq and Syria. He will then go to a NATO meeting in Brussels and a security conference in Munich.