South Korea has reaffirmed that next month's meeting of G20 leaders in Brisbane is a critical opportunity to finalise its free trade agreement with Australia.

One of South Korea's top trade officials has nominated the G20 summit as a "psychological and physical" deadline for the nation's legislators to approve the Korea-Australia Free Trade Agreement (KAFTA) domestically.

Suh Jeong-in, director-general of the Foreign Ministry's Bureau of South Asian and Pacific Affairs, said pressure was building in both South Korea and Australia for the FTA to be ratified.

"We would like to ratify the FTA with Australia before the end of this year," Mr Suh told Australian reporters at a briefing in Seoul.

"With the G20, this will be an occasion to finalise everything."

Approval of the KAFTA has been delayed in South Korea's National Assembly, which has been distracted by the complex and highly emotional investigation into the Sewol ferry disaster earlier this year.

More than 300 of the 476 people on board died - many of them children.

The complex investigation is dominating political debate, and the KAFTA is among more than 90 bills waiting for National Assembly debate and approval.

The clock is ticking on the National Assembly's approval and it appears likely that politicians might not meet the deadline for the FTA to take effect this year.

Australia's ambassador in Seoul, Bill Patterson, is working to lift the priority of the FTA, but he admitted the battle is all uphill given the profile of the Sewol disaster investigation.

"That's really the $64 million question," Mr Patterson told reporters.

"We are hopeful it (the FTA) will go through some time in the next few weeks.

"We've done everything we can, but it's a strong-willed legislature."

The financial and economic stakes are high for both Australia and South Korea.

Once the FTA is ratified, 85 per cent of Australian exports to South Korea and 90 per cent of South Korean exports to Australia will have no tariff. 

Suh Jeong-in also signalled that the threat of Ebola would be a major issue at the G20 summit.

He diplomatically defended Tony Abbott's intention not to have climate change featured as an issue for G20 leaders to discuss in Brisbane.

"Agenda setting is the chairman's prerogative" Mr Suh said in relation to Australia's current presidency of the G20. 

"When you host a G20 meeting or any other meeting, the chairman's voice is the loudest."

Source: abc.net.au