"The DPRK (North Korea) will advance along the road of bolstering up nuclear deterrent, unhindered, now that the US brings the dark clouds of a nuclear war to hang over the DPRK," Xinhua quoted a spokesperson of the North Korean foreign ministry as saying in a statement.
"There is no statute of limitations to the DPRK's declaration that it will not rule out a new form of nuclear test clarified by it in the March 30 statement. This is the exercise of the inviolable right to self-defense," the statement said.
The statement decribed Obama's four-nation Asian tour as a dangerous one as "it was aimed to bring dark clouds of more acute confrontation and nuclear arms race to Asia".
"Facts clearly prove that his tour was designed for undisguised confrontation to retain a tighter grip on allies of the US and encircle and contain its rivals in Eurasia, pursuant to the U.S. Asia-Pacific strategy for domination and scenario for aggression from A to Z," it said.
The statement said Obama's unwillingness to open talks with North Korea is tantamount to a declaration before the world that "the US hostile policy toward the DPRK remains unchanged, the US tries to bring down the DPRK by force and it began to carry out such scenario".
"His reckless acts only escalated the danger of confrontation and conflict in the Asia-Pacific region and gave further momentum to the opposition to him," it warned.
Obama will have to pay for his "reckless acts" in the mid-term elections in November, it added.
"What remains to be done by the Obama group is to watch what kind of seeds of fire sown by him this time would develop into flames that may affect the US," the statement warned.
North Korea conducted nuclear tests in October 2006, May 2009 and February 2013 respectively.