It's time to call Kim Jong Il's bluff, said The Washington Post in an editorial. The ailing North Korean leader's regime detonated a nuclear warhead in an underground test Monday, and the blast appeared larger than North Korea's first test three years ago. President Obama should respond by further isolating Pyongyang— not by lavishing attention on Kim and offering "economic and political favors."

Nuclear North Korea clearly believes it has "nothing to fear from the Obama administration for its acts of defiance," said Bahukutumbi Raman in Forbes. Obama—like Jimmy Carter—has made the U.S. look like a "confused power" with his soft policy toward Iran, his ambivalence toward terrorist-coddling Pakistan, and his silence on Myanmar's human-rights abuses. If Obama doesn't shape up, we can expect "more surprises" from rogue regimes.

Both Obama and his predecessor put North Korea "on the back burner," said Gordon G. Chang in The Wall Street Journal. The Bush administration never made nuclear "North Korea pay any price for crossing the red line of selling nuclear technology," and ended up providing Pyongyang with benefits for participating in denuclearization talks. But now "we have no choice but to respond."

Trouble is, said David E. Sanger in The New York Times, President Obama doesn't have a lot of options. International pressure won't amount to much if Obama can't "persuade Russia and China to go significantly beyond the strong condemnations" they issued Monday. But Obama must find the mix of pressure and diplomatic overtures, because Iran and other foes are watching.