With regards to the recent US move to begin the delivery of Terminal High Altitude Area Defense battery components to the South earlier this month, Moon claimed that the deployment of the THAAD should be decided upon by the new government.

On the contrary, An emphasized that the THAAD plan should be maintained considering the alliance between Seoul and Washington, while Lee reiterated that the deployment should be scrapped.

The battery emerged as one of the key issues in Northeast Asia, with Beijing rolling out various economic retaliations against Seoul in protest to the deployment.

"China's economic retaliation came as South Korea failed to make diplomatic efforts and made the decision in a hurried manner," Moon said.

Lee also said, "The THAAD does not help South Korea in terms of security," claiming the deployment of the US battery in the country is "humiliating."

"Even if the deployment began, I will return it to the original state if I became the president," Lee added.

An said his administration will deliver a message to China that the Seoul-Washington alliance will not turn its back against Beijing.

The TV debate came after the ouster of Park Geun-hye from the country's top elected office.

Park was removed from office last week due to the corruption scandal involving her confidante Choi Soon-sil. As a presidential election must be held within two months after the ouster, the presidential contenders have been stepping up campaigns on multiple fronts.

During the debate, Moon and Lee said they will put the top priority on economic recovery.

"In our country, the top 10 percent of the people take home 50 percent of the wealth. Accordingly, the majority of the middle class are faced with hardships, and our economy remains stagnant," Moon said, vowing to focus on creating more jobs to make the nation more equal and fairer.

The former party head said he would give budget priority to job creation and reduce work hours to achieve the goal of adding 810,000 public jobs and 500,000 private sector jobs.

Moon also criticized Lee's plan to adopt a basic income policy to provide support to all South Koreans in certain age groups, claiming that the country should instead focus on helping other vulnerable groups.

Lee, however, argued that providing a basic income in the form of coupons that can be used at local markets will help revitalize the economy.

An, on the other hand, said he will seek to overcome the political discord between the conservative and opposition blocs, especially as the latest corruption scandal left the nation divided.

Candidates also discussed miscellaneous issues, including Lee's criminal record of driving under the influence. Lee said he has already delivered an apology, claiming that it is up to the people to judge the case.

So far, Moon continued to stand as the most favored presidential hopeful in opinion polls.

According to the poll conducted on Saturday and Sunday by Korea Research Center, commissioned by Yonhap News Agency and KBS, Moon received an approval rating of 29.9 percent. His standing remained almost unchanged from a similar survey conducted in February.

An followed with 17 percent, while Acting President and Prime Minister Hwang Kyo-ahn, who has not yet expressed his presidential ambitions, posted 9.1 percent. Lee and Rep. Ahn Cheol-soo of the People's Party posted 9 percent and 8.4 percent, respectively.

The Democratic Party posted an approval rating of 46.4 percent, standing as the dominant player. The People's Party, which spun off from the Democratic Party, won 10.7 percent, up 1.9 percentage points on-month. The Liberty Korea Party of Park received 9.6 percent. The Bareun Party, a conservative splinter party, received 5.6 percent.

Another 23.3 percent of the respondents said they were undecided, down 1.5 percentage points from a month earlier. (Yonhap)