The United States Wednesday announced new sanctions against North Korea, targeted against its leadership, and warned of serious consequences if it again attacked the South. Relations across the divided peninsula have turned increasingly hostile after South Korea accused the North of sinking one of its warships in March, killings 46 sailors. US Secretary of State Hillary Clinton said Washington was ready to return to international talks over North Korea's nuclear weapons program if Pyongyang sent a “positive signal”, but that there had been none so far. She said the sanctions aimed to prevent North Korea selling arms and from procuring luxury goods, as well as to put out of business North Korean entities operating illicitly overseas. “We are aiming very specifically, after much intensive research built on what was done before but not limited to that, to target the leadership, to target their assets,” Clinton told a news conference in Seoul with US Defense Secretary Robert Gates after a visit to the demilitarised zone dividing the peninsula. She insisted the additional sanctions were not aimed at ordinary North Koreans, who make up one of the world's poorest societies and whose stumbling economy is already largely sealed off from the outside world because of previous punishments over nuclear and missile tests. China, the North's only major ally, expressed “deep concern” after the US and South Korea said they would start large-scale joint military drills on July 25. State television Tuesday showed the Chinese navy conducting its own exercises. “We urge relevant parties to remain calm and exercise restraint and not do anything to exacerbate regional tensions,” Chinese Foreign Ministry spokesman Qin Gang said in a statement.