North Korea tested a rocket engine Friday night in the latest of what appears to be a mounting effort by the Hermit Kingdom to develop an intercontinental ballistic missile, U.S. officials told Reuters. The engine test was North Korea’s second such launch this month. North Korea appears to have ramped up its nuclear efforts, officials say. North Korean leader Kim Jong Un boasted this month of “a new birth” in the country’s rocket program. Its recent rocket tests have violated United Nations resolutions. North Korea also recently doubled the size of its uranium-production facility, The Wall Street Journal reported this month.