Washington does not take Pyongyang's promise to halt its nuclear tests "seriously," United States President Barack Obama reportedly said on Sunday. North Korean foreign minister had earlier said the country would cease its nuclear programme if the United States suspends its annual military drills with South Korea. Pyongyang sees the military exercises in the Korean Peninsula as a threat.

The U.S. president responded to North Korea's proposal at a joint press conference held with German chancellor Angela Merkel in Hanover, according to Yonhap News Agency. "We don't take seriously a promise to simply halt until the next time they decide to do a test," Obama said.

The U.S. is ready to "enter into some serious conversations with them about reducing tensions and our approach to protecting our allies in the region" if North Korea shows it is serious about putting an end to its nuclear programmes.

"But that's not something that happens based on a press release in the wake of a series of provocative behaviours. They're going to have to do better than that. Until they do, we're going to continue to emphasise our work with the Republic of Korea and Japan, and our missile defence mechanisms, to assure that we're keeping the American people safe and we're keeping our allies safe," Obama said.

The U.S. takes all the nuclear tests, whether successful or failed, conducted by North Korea seriously, Obama said.

"What is clear is that North Korea continues to engage in continuous, provocative behavior; that they have been actively pursuing a nuclear program, an ability to launch nuclear weapons. Although more often than not they fail in many of these tests, they gain knowledge each time they engage in these tests. And we take it very seriously," he added.

North Korea on Saturday test-fired a submarine-launched ballistic missile from a 2,000-tonne Sinpo-class submarine off its east coast. While the country's leader Kim Jong Un called it a "great success," South Korean military and government sources told Yonhap the test was a failure as the missile travelled only about 30 km. The flight range was 300 km.

The communist nation is also expected to conduct its fifth nuclear test in early May. It is already facing several sanctions imposed by the United Nations and international community for the last four nuclear tests, conducted in October 2006, May 2009, February 2013 and January 2016.