Hillary Clinton speaks about national security issues at the Council on Foreign Relations in New York. (Justin Lane/European Pressphoto Agency)

LAS VEGAS -- Hillary Clinton condemned what she called North Korea's attempt to "blackmail" the world by claiming it tested a hydrogen bomb this week. She warned also that her presidential rivals' "imprudent publicity stunts" in response could risk provoking war.

In a strongly worded statement Wednesday, the former secretary of state called for immediate additional sanctions against Pyongyang.

"If verified, this is a provocative and dangerous act, and North Korea must have no doubt that we will take whatever steps are necessary to defend ourselves and our treaty allies, South Korea and Japan," Clinton said. "North Korea's goal is to blackmail the world into easing the pressure on its rogue regime."

"We can't give in to or in any way encourage this kind of bullying," she added.

Clinton said the Chinese government "must be more assertive in deterring the North's irresponsible actions." If China does not do more to halt "prohibited activities" from transpiring across its borders with North Korea, its firms should face sanctions, she said.

At a time of increased anxiety among Americans about national security, Republicans have sought to paint President Obama and, by extension, Clinton as weak. Meanwhile, Clinton has argued that she is, by far, the most experienced candidate on foreign policy issues in both the Democratic and Republican fields.

In New Hampshire this week, Clinton urged Republicans to read her book to learn about foreign policy.

"There are so many of you, you can have a book club," Clinton quipped at a town hall meeting in Derry.

The statement -- a mix of policy specifics and political red meat -- highlights Clinton's relative hawkishness on foreign policy issues compared to some of her Democratic rivals, and even some of her Republican opponents.

Clinton toes a fine line: seeking to appear aggressive on foreign policy in the face of GOP criticism, while also arguing that a Clinton presidency would expand on Obama's policies, some of which she was instrumental in putting in place as secretary of state.

In response to the apparent bomb test, Clinton used North Korea's provocations as an opportunity to highlight what she has argued is the risk of electing an inexperienced commander in chief.

“Threats like this are yet another reminder of what’s at stake in this election," Clinton noted, without addressing any specific candidates by name. "We cannot afford reckless, imprudent publicity stunts that risk war."

"We need a commander in chief with the experience and judgment to deal with a dangerous North Korea on Day One," she added.

Meanwhile, Republican candidates for president have placed the blame for the test squarely on Obama and Clinton.

"This underscores the gravity of the threats we are facing right now, and also the sheer folly of the Obama-Clinton foreign policy," Sen. Ted Cruz (R-Tex.) told reporters on Wednesday, calling for a change of course away from the current administration's foreign policy.

Ohio Gov. John Kasich charged that the Obama administration has been "asleep at the switch on North Korea."

After North Korea's claim that it tested a hydrogen bomb, The Post's Karen DeYoung explains why the U.S. response to the rogue nation is so different from how it treats Iran. (Jason Aldag,Gillian Brockell/The Washington Post)