LONDON (Reuters) - U.S. Secretary of State Rex Tillerson said on Thursday he was hopeful that China would come to its own decision to decide to use the  powerful tool  of oil supplies to persuade North Korea to reconsider its  current path . On a visit to London where he met British Prime Minister Theresa May and foreign minister, Boris Johnson, Tillerson said the United States had wanted to see a much stronger resolution from the United Nations which agreed a new round of sanctions on Monday.  It s clear that with respect to oil, and a complete embargo on oil from the U.N. Security Council, that s going to be very difficult,  he said.  In effect, that is directed at China alone because China supplies essentially all of North Korea s oil,  he told a joint news conference with Johnson.  I am hopeful that China, as a great country, a world power, will decide on their own, will take it upon themselves to use that very powerful tool of oil supply to persuade North Korea to reconsider its current path toward weapons development, reconsider its approach to dialogue and negotiations in the future.  