The U.S. will focus its efforts on shutting off North Korea’s access to crude oil, Secretary of State Rex Tillerson said yesterday at a Senate Foreign Relations committee hearing. In this, Washington will seek the assistance of other countries, Tillerson said. Imposing sanctions on countries doing business with Pyongyang is another measure that is being considered by the State Department as a means of forcing North Korea to put an end to its nuclear and missile programs. Tillerson referred to these as “secondary sanctions”, which might mean that Russia would be a target. Russian exports to North Korea in the first two months of this year shot up by 149 percent, according to Russian media reports, while China banned coal exports to its belligerent neighbor. Tillerson noted that the U.S. is working closely with China on the North Korean problem and that Beijing had “taken steps, visible steps that we can confirm,” in addressing the situation. China’s support is essential for the resolution of the North Korean problem as it provides 90 percent of North Korean imports, from crude oil and fuels to food.