The United States Secretary of State John Kerry called on China on Thursday to end “business as usual” with its ally North Korea after it defied world powers by announcing that it had tested a hydrogen bomb.
Kerry said Chinese Foreign Minister Wang Yi confirmed that China’s approach to North Korea had failed.
"China had a particular approach that it wanted to make, that we agreed and respected to give them space to implement that," Kerry told reporters.
"Today in my conversation with the Chinese I made it very clear that has not worked and we cannot continue business as usual," he added.
China has been North Korea’s main economic and diplomatic supporter although relations between the two Cold War allies have cooled in recent years.
According to data gathered by South Korea’s International Trade Association, the vast majority of North Korea’s business dealings are with China. In 2013, China bought 90 percent of the isolated country’s exports.
On Wednesday, North Korea conducted a nuclear test although the US government and weapons experts doubt Pyongyang's assertion that the device it detonated was a powerful hydrogen bomb. The test angered China, who was not given prior notice.
The US House of Representatives could vote in the coming days on a legislation backed by Republican and Democratic lawmakers to tighten US sanction on North Korea, house leaders said.
House Democratic leader Nancy Pelosi said on Thursday that Democrats would support a North Korea bill to be brought for a vote by Republicans next week. According to a congressional source, voting is expected as soon as Monday.
The House Foreign Affairs Committee passed the legislation last February, but it was on hold up until this week as the North Korean capital Pyongyang jolted the world by carrying out an underground nuclear bomb test.
House measure would target banks facilitating North Korea's nuclear program and authorize freezing of US assets of those directly linked to illicit North Korean activities. It would also penalize those involved in business providing North Korea with hard currency.
"We understand Republican leadership plans to move a bill strengthening US sanctions on North Korea. That will have strong bipartisan support," Pelosi said, adding that "we will support it."
The US and its ally South Korea are limited in their military response as it is unclear how more sanctions would deter North Korea, which has not paid heed to international pressure as it carried out four nuclear tests since 2006.
A South Korean military official said that Seoul and Washington discussed the deployment of US strategic assets on the divided Korean peninsula without giving further details.
However, White House spokesman Josh Earnest said that there had been no discussion or talk with South Korea about any introduction of the so-called Terminal High Altitude Area Defense (THAAD) system, a move opposed by China.
"There have been no discussions or consultations with the South Koreans" about the deployment of anti-ballistic missile capability," Earnest said.
THAAD system includes radars that can track multiple ballistic missiles up to 2,000 km (1,200 miles) away, a range which could reach deep into China.