China urged the United States and North Korea on Tuesday to "seize the moment" and take positive steps so that six-party talks on the North's nuclear program can resume quickly. China's UN Ambassador Zhang Yesui, who took over the rotating presidency of the Security Council this month, called recent talks between senior US and North Korean officials a "positive development." At a news conference Tuesday, Zhang said the most important thing now is for the key parties to "seize the moment and take some positive efforts and meet each other halfway so that ... the six-party talks will start as soon as possible." Washington and Pyongyang agreed after last month's meeting in Pyongyang on the need to resume the stalled six party talks. But the North cautioned that there are still unspecified differences to be resolved and did not make a firm commitment on when it would rejoin the negotiations with the US, Russia, China, South Korea and Japan. North Korea quit the talks in April in anger over a UN rebuke after it launched a long-range rocket. In May, it conducted a second nuclear test, promoting the Security Council to impose tough new sanctions, including a ban on all arms exports. The impoverished nation is believed to earn hundreds of millions of dollars every year by selling missiles, missile parts and other weapons to countries such as Iran, Syria and Myanmar. When US Ambassador Stephen Bosworth, the special US envoy to North Korea, visited Pyongyang in December he said the North lobbied to have the sanctions eased. But Bosworth said that wouldn't happen until North Korea came back to nuclear negotiations and made significant progress on getting rid of its atomic weapons. The talks began in 2003, and in 2005 there was agreement on a disarmament pact which calls for North Korea to end its nuclear programs in exchange for economic aid, security assurances and diplomatic recognition. The United States wants to see verifiable and irreversible steps to implement the agreement. After Bosworth's visit, Chinese Vice President Xi Jinping, a rising star in the country's leadership, called for efforts to quickly resume the six-party talks, which Beijing hosts. He also said China wants to work closely with South Korea to advance the denuclearization process on the Korean peninsula. "As far as China is concerned," Zhang said, "we have consistently emphasized that the Korean peninsula should be denuclearized in the interest of maintaining peace and stability in the peninsula and northeast Asia." "We also believe that the questions should be solved through dialogue and through peaceful means," he said.