The White House has accused Beijing of supplying North Korea with technology for a missile launcher showcased in a military parade in Pyongyang last week.
"We've raised the allegations with the Chinese government ... as part of our ongoing close consultations on North Korea," White House spokesman Jay Carney said at a daily news briefing on Monday.
Carney was reacting to reports that the vehicle, a transporter-erector launcher, may have been of Chinese origin.
Senior U.S. officials believe the Chinese company Hubei Sanjiang sold components used in constructing the launcher, the Wall Street Journal reported.
The launcher was seen carrying what appeared to be the North's latest missile.
China's involvement would constitute a breach of a UN arms embargo.
China has said it did not violate UN resolutions on North Korea.
Last week, the defense publishing group Jane's said the UN Security Council was investigating the claims.
Carney's comments come amid increased tensions on the Korean peninsula, following Pyongyang's failed long-range rocket launch earlier this month which the United States said was cover for a ballistic missile technology test.
Western nations fear the North may be preparing for another nuclear test.
Carney said the United States would "continue to work with the international community, including China, to enforce sanctions against North Korea's ballistic missile program and nuclear program."
Meanwhile, Chinese President Hu Jintao reaffirmed stong ties with Pyongyang during a meeting in Beijing on Monday with a North Kokean envoy, and appealed for "peace and stability" on the Korean peninsula.
"We will... strengthen strategic links and coordination on major international and regional issues for the purpose of safeguarding lasting peace and stability of the Korean peninsula," Hu was quoted by Xinhuia news agency as saying.
The North has threatened to wage a "sacred war" against Seoul over what it said where South Korean President Lee Myung-bak's "insulting" remarks about celebrations of the centenary of the birth of its late founding leader Kim Il-sung.
South Korea said last week it had deployed new cruise missiles capable of hitting anywhere in the North.
