South Korea has given China the complete technical report on the sinking and has said it is open to a Chinese delegation coming to inspect the shattered hull and corroded torpedo retrieved from the seabed.
On Saturday, Mr Wen will have a trilateral summit with Mr Lee and Japan’s prime minister, Yukio Hatoyama, on the South Korean resort island of Jeju. Japan and South Korea have been expected to push for assurances at this meeting that Beijing will not block action at the UN Security Council, although Seoul accepts Beijing may never be able to rebuke Pyongyang publicly.
While further sanctions were still possible, a senior South Korean official said Seoul was not expecting Beijing to rebuke Pyongyang but hoped it would not veto UN action. While tougher sanctions were theoretically possible, the official stressed Seoul’s priority was to garner a strongly worded international condemnation on moral grounds.
In practical terms, he told foreign reporters there was little room to tighten sanctions and that it would be far more effective if the international community were to implement existing sanctions more rigorously, to target Pyongyang’s missile and nuclear weapons programme.
China is Pyongyang's economic lifeline. It props up the ailing regime through fear that a collapse will trigger a refugee crisis and unrest in the world's most militarised society.
The South Korean official also said the government was raising its guard against terrorist attack, given that Pyongyang seemed to be reverting to shock tactics. The last big North Korean attack was the bombing of a South Korean airliner in 1987, which killed 115 people.
The official said the government was most concerned that North Korea could launch an attack while South Korea hosts international summits during its presidency of the G20 group of leading economies this year.
He said South Korea’s security forces were targeting internet users who were being used by Pyongyang to spread dissent, a process he referred to as “infiltration”.
When asked whether he had sensed any direct indication of an attack being co-ordinated in cyberspace, he replied: “Not yet, but we are cautious about it. We want to occupy that area before infiltration.”
Policing the internet is a sensitive issue and the South Korean government has received strong international criticism for reducing internet freedoms. Seoul argues that its measures are a strategic necessity as Pyongyang reverts to more brutal tactics.