BEIJING -- Hours after carrying out a nuclear test in defiance of international warnings not to, North Korea warned Tuesday that it will take new unspecified actions if the United States doesn’t curb its hostility toward the rogue nation.

In a statement it attributed to the country’s Foreign Ministry, the North Korean state news agency blamed the United States for U.N.-imposed sanctions intended to discourage North Korea’s missile and nuclear development programs. A continuation of that approach, the statement said, would leave North Korea “with no option but to take the second and third stronger steps.”

South Korea’s intelligence service warned that its northern neighbor might conduct another nuclear test and might repeat its December launch of another long-range missile.

The threats came as scientists began analyzing data from the test to determine the strength of the explosion and what it might portend about the country’s ability to accumulate a nuclear arsenal. The U.N. agency that’s charged with monitoring nuclear tests around the world said Tuesday’s blast was at least twice as powerful as one the North Koreans set off in 2009 and “much larger” than the country’s first test, in 2006.

North Korea official state news media described the device as “small and light,” characteristics that seemed to indicate it could be used atop a rocket or missile, a step that would put countries such as Japan and even parts of the United States within range.

Meeting in New York, the U.N. Security Council condemned the test, calling it "a clear threat to international peace and security." President Barack Obama also denounced the test, as did a wide range of foreign governments.

U.S. Rep. Ed Royce, R-Calif., the chairman of the House Foreign Affairs Committee, called on the Obama administration to take tougher steps against North Korea, noting that the country also had launched a multi-stage rocket in December and had posted a bizarre video on the Internet that shows a sleeping North Korean dreaming of a nuclear attack on New York.

"The administration must replace its failed North Korea policy with one that is energetic, creative and focused on crippling the Kim regime’s military capabilities," Royce said in a statement, referring to North Korean leader Kim Jong Un. "Otherwise, the grave North Korean threat to the region and the United States will only grow.”

It wasn’t at all clear what those tougher steps might be. The United States and the United Nations already have placed North Korea under a wide range of economic sanctions, and stronger steps, such as a naval blockade, would need the agreement of North Korea’s principal ally, China.

How willing – and able – China would be to impose tougher measures remains to be seen. China repeatedly has admonished its neighbor from conducting such a test, apparently to no avail.

Chinese Foreign Minister Yang Jiechi summoned the North Korean ambassador to Beijing, warning him that China was “strongly dissatisfied” with the nuclear test and calling on Pyongyang to refrain from actions that might worsen the situation, according to a ministry news release.

But the wording of a statement the Foreign Ministry issued in Beijing condemning North Korea’s actions mirrored that of 2009, when North Korea staged a previous test and wasn’t cast away by China. It made no threat of sanctions or other consequences and urged “all parties to respond in a cool-headed manner” through dialogue.