SEOUL: China's envoy for the North Korean nuclear issue arrived in the capital, Pyongyang, on Tuesday, the North's KCNA news agency reported, amid a push by the United States and South Korea for tougher sanctions on the North after its fourth nuclear test. China's Special Representative for Korean Peninsula Affairs Wu Dawei was expected to hold discussions with the North Koreans on the nuclear issue after his arrival there, Japan's Kyodo news agency reported from the North Korean capital. Neither Kyodo nor KCNA gave further details. China's foreign ministry did not have immediate comment. North Korea is believed to be making preparations for a test launch of a long-range rocket, US officials have said, after activity at its test site was observed by satellite. North Korea has said it has a sovereign right to pursue a space program by launching rockets. But the United Nations see that activity as a missile program in disguise. South Korea's Yonhap news agency reported on Monday that Wu met his U.S. counterpart, Sung Kim, last week following US Secretary of State John Kerry's visit to Beijing. Wu met his South Korean counterpart last month. Kerry and Chinese Foreign Minister Wang Yi last Wednesday agreed on the need for a significant new UN Security Council resolution against the North, but there were few signs of progress on agreeing on the details. Wang rejected as 'groundless speculation' remarks by US officials that China, using its influence as the North's main economic benefactor and political backer, could do more to press North Korea and must end 'business as usual'. China disapproves of the North's nuclear program and says it is making great efforts to achieve denuclearisation on the Korean peninsula. Pressure grew on China after the North detonated a nuclear device on Jan. 6, calling it a successful hydrogen bomb test, although the claim was met with scepticism by US and South Korean officials and nuclear experts, who said the blast was too small for it to have been a full-fledged hydrogen bomb. North Korea is already under a wide array of international sanctions for its nuclear program. The US House of Representatives responded to the latest test with a vote last month to pass legislation that would broaden sanctions.