About 18000 soldiers have applied to join the contingent, more than five times the 3585 troops South Korea intends to send to Iraq, an army spokesman said.
By next Tuesday when the 15-day recruitment period expires, the total number of applicants is expected to pass 30,000, he said.
Rank and file troops who serve in the new contingent will receive 2.1 million won (1,800 dollars) as a monthly bonus, the army said.
South Korean conscripts normally receive up to 26,950 won monthly during their obligatory two-year military service.
South Korea has announced plans to send more than 3000 troops to Iraq, mostly medics, construction engineers, transport and logistics workers, in April. The National Assembly must first approve the plan.
The decision to send troops to Iraq followed a US request in
September that sparked protests from South Korean opponents of the Iraq war.
Public opinion was further polarized after a deadly ambush in Iraq on November 30 which left two South Koreans dead and two injured.