The nationally televised Republican debate in New Hampshire began minutes after the news of North Korea's rocket launch, and the candidates all responded.
Current frontrunner Donald Trump, a real estate tycoon, said he believed China had "tremendous control" over North Korea, adding that he based his opinion on conversations he had had with bankers and others he's dealt with.
Florida Sen. Marco Rubio, who polls suggest would be the Republicans' best bet as presidential candidate, also said he thought the United States could leverage its relationship with China to keep North Korea in check.
However, Rubio, 44, faced a number of attacks from his rivals, who challenged his readiness to be president. Former federal prosecutor and New Jersey Governor Chris Christie said, "You have not been involved in a consequential decision where you had to be held accountable, you just simply haven't."
Texas Sen. Ted Cruz, an evangelical who won the Iowa caucuses, also came under withering criticism for controversial political tactics, with one candidate disparaging him for having "Washington ethics" and being willing to test the campaign's legal limits.
Waterboarding in question
Trump was the most direct in promising to use the controversial technique if elected president, but Cruz said he wouldn't rule out using the tactic, which simulates drowning.
Former Florida Governor Jeb Bush, meanwhile, said he agreed with the existing ban on waterboarding, while Rubio said it was inappropriate to discuss interrogation tactics.
Differences over immigration
On the subject of immigration, Ohio Governor John Kasich said he "couldn't even imagine" ripping families apart by deporting immigrants living in the country illegally and that doing so did not match American values.
Kasich is at odds with several of his rivals, including Cruz, on the issue of deportation. Cruz said it was possible to deport people living here illegally. The only thing missing, he said, was "political will."
The New Hampshire primary will take place on Tuesday, February 9.
av/tj (AP, AFP)