South Korea is planning to hold more military exercises, after its joint naval manoeuvres with the United States end in the Yellow Sea on Wednesday.
Seoul officials said they were in talks with Washington to stage further naval drills, possibly as soon as this month.
A US aircraft carrier arrived in the region last week shortly after the North shelled a South Korean island.
Four people died in the attack. China is under pressure from the US to exert influence over its ally North Korea.
Unconfirmed reports from Beijing say that China's state councillor Dai Bingguo had been invited to the North Korean capital, Pyongyang.
At the same time, North Korea's Choe Thae-bok, an aide to leader Kim Jong-il, is in Beijing.
China has called for an emergency meeting of members of the six nations involved in talks on North Korean nuclear disarmament.
The AFP news agency reports that China has blocked any formal UN censure of North Korea for last week's shelling.
Stalled talks
A South Korean Joint Chiefs of Staff officer said that Seoul and Washington were planning new military drills off South Korea's west coast.
The officer, speaking on condition of anonymity, said talks were focused on whether these would take place this month or next.
Separately, South Korea is planning what it calls routine week-long naval live-fire exercises from 29 sites around the country.
These are due to start next week and continue for several weeks.
China, however, has expressed its anger at the joint US-South Korean military exercises - which were planned before North Korea's shelling of Yeonpyong island last week.
Washington says the drills are purely defensive in nature.
China has also been pressing for a resumption of the six-nation talks on ending North Korea's nuclear programme.
The US has said these talks cannot resume until North Koreas apologises for its torpedoing of a South Korean warship in March, and stops further nuclear enrichment plants from operating.
The six-party talks, involving the two Koreas, the US, China, Japan and Russia, have been stalled since April 2009.
Analysts say diplomacy has been further complicated by the recent leak of diplomatic cables by whistle-blowing website Wikileaks.
North Korea: Timeline 2010
26 March: South Korean warship, Cheonan, sinks, killing 46 sailors
20 May: Panel says a North Korean torpedo sank the ship; Pyongyang denies involvement
July-September: South Korea and US hold military exercises; US places more sanctions on Pyongyang
29 September: North holds rare party congress seen as part of father-to-son succession move
29 October: Troops from North and South Korea exchange fire across the land border
12 November: North Korea shows US scientist new - undeclared - uranium enrichment facility
23 November: North shells island of Yeonpyeong, killing at least four South Koreans
Link