Washington: US President Donald Trump on Monday vowed to deal with North Korea "very strongly", calling the Asian country a "big, big problem".Trump made the remark at a joint press conference with visiting Canadian Prime Minister Justin Trudeau, after North Korea test-fired a ballistic missile on Sunday. But the US President did not elaborate on what actions he planned to take in relation to the Asian country, Xinhua news agency reported."We have problems all over the Middle East. We have problems just about every corner of the globe no matter where you look," Trump said when asked about the most important national security issues facing the United States.On Monday, the Pentagon strongly condemned North Korea's ballistic missile launch and vowed to "take all necessary measures to deter and defeat threats to US and ally territories and citizens"."The North American Aerospace Defence Command determined the missile launch did not pose a threat to North America," said Jeff Davis, a spokesman for the US Department of Defence. "We also worked very quickly with our Japanese and South Korean allies to make sure it did not pose a threat to them either."On Saturday, Trump vowed US support to Japan in a hastily called joint press conference with visiting Japanese Prime Minister Shinzo Abe in Florida. "I just want everybody to understand and fully know that the United States of America stands behind Japan, its great ally, 100 per cent," Trump said.North Korea claimed on Monday it had successfully test-fired Pukguksong-2, a surface-to-surface medium-to-long-range ballistic missile, and its top leader Kim Jong Un guided the test firing, according to the state news agency KCNA.Earlier Monday, UN Secretary-General Antonio Guterres, in a statement issued by his spokesman, strongly condemned the latest move by Pyongyang, saying "this action is a further troubling violation of (UN) Security Council resolutions".