Republicans blame US President for North Korea nuclear advances

Republican U.S. presidential candidates on Wednesday faulted President Barack Obama's "feckless" and "failed" foreign policy for letting North Korea bolster its nuclear arms capabilities, while also blaming Democratic front-runner Hillary Clinton.

The Republicans, who often criticize Obama's handling of foreign affairs including Syria's civil war, the rise of Islamic State and the agreement to curb Iran's nuclear program, made their comments after North Korea said it tested a miniaturized hydrogen nuclear device on Wednesday. The United States expressed doubts about North Korea's claim.

Clinton, who served as Obama's secretary of state from 2009 to 2013, condemned North Korea's move as a "dangerous and provocative act" and said the United States should respond with more sanctions and stronger missile defenses. She also defended her performance as Obama's top diplomat.

"As secretary, I championed the United States' pivot to the Asia Pacific - including shifting additional military assets to the theater - in part to confront threats like North Korea and to support our allies," Clinton said in a statement. "I worked to get not just our allies but also Russia and China on board for the strongest sanctions yet."

Businessman Donald Trump, leading the race for the Republican nomination in November's election, urged China to rein in its ally North Korea or face trade repercussions.

"China should solve that problem," Trump said on Fox News.

"And if they don't solve the problem, we should make trade very difficult for China. ... North Korea is totally under their control. Without China, they wouldn't eat," added Trump, who called North Korean leader Kim Jong Un a madman.

Jeb Bush, whose brother George W. Bush was president when North Korea conducted its first nuclear test in 2006, said on Twitter: "North Korean nuke test shows danger of continuing feckless Obama/Clinton foreign policy." North Korea has carried out three nuclear tests since.

Texas Senator Ted Cruz blamed North Korea's test on the "folly" of failed policies by Obama and Clinton. Cruz said as president he would "rip to shreds" the international agreement on Iran's nuclear program and predicted if Clinton is elected in November Iran would detonate a nuclear weapon, "sadly not as a test," over a city like Tel Aviv, New York or Los Angeles.

North Korea's test was "the latest example of the failed Obama-Clinton foreign policy," Florida Senator Marco Rubio said. "I have been warning throughout this campaign that North Korea is run by a lunatic who has been expanding his nuclear arsenal while President Obama has stood idly by."

"The Obama administration has been asleep at the switch on North Korea, and that inaction has allowed serious and destabilizing actions like this to occur," Ohio Governor John Kasich added.

Kentucky Senator Rand Paul advocated drawing on China's influence with North Korea and possibly increasing sanctions on the isolated communist state.

"There are no easy solutions," Paul told CNN. "You want me to magically wave a wand and all of a sudden their nuclear weapons are gone?"

Clinton's closest Democratic challenger, Vermont Senator Bernie Sanders, said the first U.S. step should be to "lean on" China to push North Korea to start adhering to international agreements.