The United States has warned China it will blacklist Chinese companies and banks that do illicit business with North Korea if Beijing fails to enforce UN sanctions against Pyongyang.<br/><br/>US National Security Adviser Susan Rice and Secretary of State John Kerry stressed the importance of choking off financial flows to Pyongyang during a meeting with Chinese State Councilor Yang Jiechi in New York. In response to the US warning, Chinese officials said they believe pressure alone on North Korea will not work, and that they oppose any US action that would hurt Chinese companies.<br/><br/>The UN Security Council, which includes China, unanimously voted to impose new, tougher sanctions on North Korea on Wednesday, to cut its annual export revenue by a quarter in response to the September nuclear test. North Korea has rejected the resolution.<br/><br/>