The top United States military officer has called on China to intensify pressure on North Korea, saying Beijing was wrong if it thought the leader Kim Jong-il was controllable.
China has said it is determined to prevent an escalation of this week's violence on the Korean peninsula after North Korea shelled a South Korean island, the heaviest bombardment since the 1950-53 Korean War.
A nationally-televised funeral took place in South Korea on Saturday for two marines killed in the attack. Two civilians also died.
But Admiral Mike Mullen, chairman of the US Joint Chiefs of Staff, says North Korea's nuclear ambitions increase the threat of regional instability and that it is hard to know why China doesn't push harder.
Beijing has warned against military acts near its coast as US and South Korean forces prepare for four days of naval drills in the Yellow Sea starting on Sunday.
Government officials say China's priority is to prevent a recurrence of Tuesday's attack on the island of Yeonpyeong.
In a statement, the ministry said: The top priority now is to keep the situation under control and to ensure such events do not happen again.
The US commander in South Korea, General Walter Sharp, has called on the North to stop its attacks.
General Sharp said Tuesday's attack was a clear violation of the 1953 armistice.
The George Washington was previously deployed to South Korean earlier this year, following a rise in tensions after the sinking in March of a South Korean warship, the Cheonan - which was widely blamed on the North.