North Korean leader Kim Jong Un guides on the spot the underwater test-fire of strategic submarine ballistic missile in this undated photo released by North Korea's Korean Central News Agency (KCNA) in Pyongyang on April 24, 2016. KCNA/viaNorth Korea appears to be preparing a test-launch of an intermediate-range ballistic missile, South Korea's Yonhap news agency said on Tuesday, after what the United States described as the "fiery, catastrophic" failure of the first attempt.
Separately, President Barack Obama said the United States is working on defending itself and its allies against potential threats from what he called an "erratic" country with an "irresponsible" leader.
On April 15, the North failed to launch what was likely a Musudan missile, with a range of more than 3,000 km (1,800 miles), meaning it could, if launched successfully, hit Japan and also theoretically put the U.S. territory of Guam within range.
The Musudan missile, which can be fired from a mobile launcher, is not known to have been successfully flight-tested.
In a CBS interview that aired on Tuesday, Obama said the United States "is spending a lot more time positioning our missile development systems, so that even as we try to resolve the underlying problem of nuclear development inside of North Korea, we're also setting up a shield that can at least block the relatively low-level threats that they're posing now."
North Korea tested its fourth nuclear bomb on Jan. 6 and launched a long-range rocket on Feb. 7, both in defiance of U.N. resolutions. On Saturday, the North conducted a test of a submarine-launched ballistic missile.
"There are indications that the North may fire a Musudan missile that it launched and failed on Kim Il Sung's birthday on April 15," Yonhap quoted an unnamed government official as saying. Kim Il Sung is the North's founder.
North Korea needs a "powerful nuclear deterrence" to counter U.S. hostility and threats, North Korea's foreign ministry was quoted by the state news agency KCNA as saying on Tuesday.
"The U.S. continued pursuance of extreme hostile policy and nuclear threat and blackmail against the DPRK will only make the latter make drastic progress in bolstering nuclear attack capabilities," KCNA quoted a ministry spokesman as saying.
North and South Korea remain technically at war after their 1950-53 conflict ended in a truce, rather than a treaty. The North, whose lone major ally is neighbor China, routinely threatens to destroy South Korea and its major ally, the United States.
Obama said there "was no easy solution" to the North Korean threat, adding that while the United States "could destroy North Korea with our arsenals" there would not only be humanitarian costs but also a potential impact on South Korea.
The April 15 failure was seen as an embarrassing blow for current leader Kim Jong Un, Kim Il Sung's grandson, who has claimed several advances in weapons technology in recent months and is widely expected to conduct a fifth nuclear test soon.
South Korean Defence Ministry spokesman Moon Sang-gyun declined to confirm the Yonhap report but said the North's military would likely spend some time trying to fix the problem following the failed launch.
Experts see North Korea's Musudan test as part of an effort to develop an intercontinental ballistic missile that can reach the mainland United States.
"They are erratic enough, their leader is personally irresponsible enough that we don't want them getting close" to obtaining such weapons, Obama told CBS.
North Korea said its nuclear test in January was a hydrogen bomb, although that claim has been disputed by foreign governments and experts given the relatively small size of the blast.
North Korea said its submarine-launched ballistic missile test on Saturday was a "great success" that provided "one more means for powerful nuclear attack".
South Korea on Tuesday described the test, which sent a missile traveling about 30 km (18 miles), as a partial success.
The United States and South Korea began talks on possible deployment of a new missile-defense system, the Terminal High Altitude Area Defense (THAAD), after the latest North Korea nuclear and rocket tests.
Expanded U.N. sanctions aimed at starving North Korea of funds for its nuclear weapons program were approved in a unanimous Security Council vote in early March on a resolution drafted by the United States and China.
(Reporting by Jack Kim in Seoul; Additional reporting by Susan Heavey in Washington and Dominic Evans in London; Editing by Nick Macfie and Raissa Kasolowsky)