US says China needn't fear missile defence for South Korea

China has no need to be worried about U.S. plans to deploy a new anti-missile system in South Korea to protect it from North Korea, a senior U.S. diplomat said on a visit to Beijing, adding North Korea had shown no interest in diplomacy.

The United States and South Korea have begun talks on possible deployment of the Terminal High Altitude Area Defense (THAAD) system after North Korea tested its fourth nuclear bomb on Jan. 6 and launched a long-range rocket on Feb. 7, both in defiance of U.N. resolutions, but China firmly opposes the move.

"The fact is that North Korea presents a very serious missile threat to the Korean peninsula," Sung Kim, the U.S. special envoy for North Korea, told reporters.

"And we, together with South Korea, have decided that we should take appropriate defensive measures to protect ourselves against this missile threat from North Korea."

Kim said the United States remained open to credible and meaningful diplomacy with North Korea, but the country had shown no interest.

North and South Korea remain technically at war after their 1950-53 conflict ended in a truce, rather than a treaty. The North, whose lone major ally is neighbour China, routinely threatens to destroy South Korea and its major ally, the United States.

The North Korean threat was why "we have started formal consultations about the possibility of deploying the THAAD system on the peninsula", Kim said.

North Korea has vowed to conduct further nuclear tests, despite stepped up international sanctions.

Satellite images show that North Korea may have resumed tunnel excavation at its main nuclear test site, similar to activity seen before the January test, a U.S. North Korea monitoring website reported on Wednesday.

Kim said he had no definitive information a fifth test was coming, and that he was not sure China knew either.

China is North Korea's most important economic and diplomatic backer, but has been infuriated by North Korea's nuclear and missile tests and has signed on for tough U.N. sanctions.

The effectiveness of current or any new sanctions depends heavily on them being fully implemented by China, U.S. officials and analysts say.

Kim said China had taken "a number of steps toward implementation" of the latest sanctions resolution.

"I hope and I expect that China would take its responsibility very seriously and actually implement all provisions of this unprecedented resolution," he added.

China says it has a right to develop what it calls "normal relations" with North Korea.

North Korea became China's second-biggest coal supplier in March, with deliveries up 80.6 percent from a year ago to 2.35 million tonnes, data from China's customs authority showed on Thursday.

China's Ministry of Commerce announced at the beginning of April that it would ban North Korean coal imports to comply with new U.N. sanctions. But it would make exceptions for coal delivered via North Korea's Rason port from third countries, and for exports intended for "the people's well-being" and not connected to nuclear or missile programmes.