Last week a team of international investigators concluded that the ship was hit by a North Korean torpedo, a charge North Korea has denied.
The findings have dramatically raised tensions on the Korean peninsula, with North Korea suspending most of the few links it has with the South, claiming Seoul fabricated evidence related to the sinking.
China has so far refused to back calls for further sanctions against the North, and has avoided giving its support to the investigation team's findings.
"South Korea will focus all diplomatic efforts on holding North Korea responsible in the summit this weekend," Park Sun-Kyoo, spokesman for the South Korean president, told reporters ahead of the meeting.
During talks on Friday, the Chinese premier was quoted as saying that Beijing would review the probe results in an "objective and fair" manner before determining its position.
Wen added that Beijing would not protect those responsible.
South Korea, the US and Japan are all seeking China's support for motion to sanction - or, at least, to censure - North Korea at the UN Security Council.
China, which holds veto power at the Security Council, is the North's sole major ally and economic lifeline.
Al Jazeera's Tony Birtley, reporting from Seoul, said that Wen's position was no surprise. "He spoke the words that people expected but didn't want to hear. There was some flawed hope that maybe Premier Wen would come out and stand behind the international community to have some sort of action that would go through the security council and probably help to dissipate this crisis, but he didn't."
In its latest comments on the sinking, North Korea on Friday again flatly rejected allegations that it torpedoed the Cheonan, saying it does not own a midget submarine allegedly used for the attack, according to Pyongyang's official news media.
|Wen, left, said China would not protect whoever sunk the Cheonan [AFP]
Major General Pak Rim Su, director of the policy department of the North's powerful National Defence Commission (NDC), also rebutted Seoul's claim that parts of a torpedo salvaged from the seabed exactly match a model that the North had offered for export.
"Who in the world would hand over torpedo designs while selling torpedoes?" Pak said.
South Korea's reprisals against the North include a trade cut-off and the resumption of cross-border propaganda broadcasts.
Pyongyang has threatened to shell the loudspeakers now being installed along the tense frontier if the broadcasts go ahead.
The North has also cut all ties with the South, scrapped pacts aimed at averting accidental flare-ups along their disputed sea border and vowed to attack any intruding ships.