The United States kept a wary eye on North Korea after the reclusive state's unsuccessful launch of a long-range rocket and President Barack Obama said on Friday Pyongyang faced further isolation if it continued to defy the international community.

The White House suspended a deal to provide significant food aid to North Korea following the rocket launch, which it had warned Pyongyang against. U.S. officials also consulted other powers, including North Korean ally China, on how to respond.

Obama said he was deeply concerned by North Korea's rocket launch, which violated U.N. Security Council resolutions, although he noted that "they've been trying to launch missiles like this for over a decade now and they don't seem to be real good at it.

"We will continue to keep the pressure on them and they'll continue to isolate themselves until they take a different path," Obama said in an interview with Telemundo.

North Korea acknowledged that its much-hyped long-range rocket launch failed. The United States and Japan said the rocket crashed into the sea after traveling a much shorter distance than a previous North Korean launch.

While the White House left the door open a crack to further talks with North Korea, the launch attempt in defiance of international pressure appeared to sideline for now Obama's hopes for engagement and usher in a new round of tensions.

A U.S. official warned that Pyongyang faced additional sanctions if it defied the international community again.

"If they continue to take additional provocative actions, we of course have to continue to look at ways in which we could tighten sanctions on the North Koreans, and take additional steps to apply pressure on the regime," White House National Security Council spokesman Ben Rhodes said.

Officials and analysts worried that embarrassment from the rocket's failure might spur North Korea to undertake a third underground nuclear test or other actions to buttress the rule of the North's young new leader, Kim Jong-un, son of former leader Kim Jong-il.

The Pentagon said it was keeping an eye on North Korea. "It's not just about missiles. It's about other things that they have and might do," Pentagon spokesman George Little told reporters, saying he could not confirm any underground nuclear test preparations in North Korea.

A U.S. official said the North's decision to acknowledge the rocket failure probably reflected the international media's presence in the country to witness the launch, "but also may indicate a degree of self-confidence on the part of leadership" and a desire to conduct such tests more regularly.

The official, who spoke on condition he not be named, also acknowledged the limits of U.S. intelligence about North Korea, saying it was "just impossible to really know" why Pyongyang admitted the failure.

An analysis of satellite images from North Korea suggested that preparations for a third nuclear test were under way, said James Hardy, Asia Pacific Editor of IHS Jane's Defence Weekly.

Pyongyang said the rocket launch was to put a satellite in orbit, but Washington and Tokyo described it as a disguised missile test.

The U.N. Security Council deplored the rocket launch, but said it would continue talks on an appropriate response, U.S. Ambassador to the United Nations Susan Rice said in New York.

DELIVERING A MESSAGE

Rhodes said Washington would not go forward with a February 29 deal to provide North Korea with nutritional aid in return for its suspension of uranium enrichment activities and other movement toward the denuclearization of the Korean peninsula.

The United States has insisted that the rocket launch was banned under that deal. North Korea said it was not.

The State Department said the food aid deal was "suspended" and that constructive engagement with North Korea was still possible if it were reciprocated by Pyongyang.

"But as we've said many times, we're not going to reward bad behavior with engagement," spokesman Mark Toner said.

Secretary of State Hillary Clinton spoke about the rocket launch on Friday with China's foreign minister, Yang Jiechi. "We're asking them to use their relationship with North Korea to convey our concern about their recent actions," Toner said.

Beijing, while making clear it was displeased with North Korea's behavior, generally opposes sanctions and other measures it sees as confrontational.

Jack Pritchard, president of the Korea Economic Institute and a former U.S. nuclear negotiator, said Pyongyang would need a "spectacular achievement to overcome the national embarrassment it finds itself in now."

"What that means is that it is now much more likely that North Korea will move forward with its third nuclear test," he said.

Richard Haass, president of the Council on Foreign Relations, said it was likely the principal reason for the launch was to consolidate the authority of its new leader, Kim.

"There is thus a real risk that he will turn to a tried and true path to accomplish the same ends. If history is any guide, this suggests that a test of a nuclear warhead or some sort of aggressive military action - for example, an artillery strike - against South Korea could be in the offing," he said.

"And if this latter scenario occurs, South Korea, unlike on previous occasions, is almost certain to retaliate," Haass wrote on CFR's blog.