SEOUL, South Korea (AP) -- President Barack Obama warned North Korea on Saturday that the United States "will not hesitate to use our military might" to defend allies, as he sought to showcase U.S. power in the region amid China's growing influence and Pyongyang's unpredictable nuclear threats.
Obama's visit to Seoul comes as North Korea has threatened to conduct its fourth nuclear test, leading Obama to raise the possibility of further sanctions.
The website 38 North, which closely monitors North Korea, said commercial satellite imagery from Wednesday showed increased movement of vehicles and materials near what are believed to be the entrances to two completed tunnels at Punggye-ri nuclear test site. The movements could be preparations for an underground atomic explosion, although predicting underground tests is notoriously difficult.
Obama ridiculed North Korea's attempt to show force. "Anybody can make threats," he said. "Anyone can move an army. Anyone can show off a missile. That doesn't make you strong."