SEOUL, Aug. 18 (Xinhua) -- South Korean President Lee Myung-bak cast an absentee ballot Thursday prior to a controversial Seoul- wide referendum on free school meals.

"Voting is an important right and duty in a democratic country. I wanted to express my opinions through voting," Lee said, according to his office Cheong Wa Dae.

The president and first lady Kim Yoon-ok are scheduled to begin a Central Asian trip on Sunday.

The referendum next Wednesday is to decide whether to uphold the opposition-dominated city council's decision last December to provide free meals at all elementary schools in South Korea's capital city starting later this year.

The city council, controlled by the biggest opposition Democratic Party, wants to expand the program to include all middle school students from 2012.

Conservative Seoul mayor Oh Se-hoon, backed by the ruling Grand National Party, downplays the plan as "welfare populism" and has offered an alternative plan aimed at providing free meals to students from low income families starting in 2014.

Critics of the mayor, who was reelected last year for a second term in office, say Oh's plan will stigmatize children and call for boycott of the referendum. Oh's attempt to scrap the city council's plan requires a voter turnout of 33.3 percent or higher and a majority approving the mayor's alternate plan.

President Lee, Oh's predecessor, has repeatedly voiced opposition to what he calls populist policies espoused by his liberal opponents.