President Obama arrived in Seoul, South Korea, Friday to news that North Korea may be counting down to a nuclear weapons test.
Such moves out of Pyongyang are no surprise and are typical for the North's behavior, Obama told reporters while in Tokyo, his previous stop on his Asia trip.
The President said he is prepared to deliver a firm response, if a test is conducted during his visit.
North Korea's heightened activity at its nuclear test site was already known. But now the final step needed for an underground detonation has been taken, a South Korean government official said Thursday.
The North has closed off the entrance to the tunnel at the Punggye-ri nuclear test site, the official said.
That gives Pyongyang 11 days to either detonate a nuclear device or cancel the test. It would be the North's fourth test of a nuclear weapon.
We're expecting a live news conference from the President within the hour. We'll bring it to you when it starts on "Early Start."
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