The ruling Saenuri Party on Tuesday pressed popular software developer and science scholar Ahn Cheol-soo to come clean on his presidential ambitions amid growing media speculation he has decided to run for the top office.

Ahn, 50, has been widely considered a potential opposition candidate in December's presidential vote since he demonstrated powerful influence over voters during October's Seoul mayoral by-election. But the soft-spoken professor of Seoul National University has never made his intentions clear.

On Monday, the newspaper JoongAng Ilbo reported that Ahn "firmed up" his mind to seek the presidency and asked an unidentified senior opposition politician to join his camp. Ahn plans to act independently rather than entering existing parties, the report said.

Ahn has stuck to silence about the report.

His participation in the presidential race is expected to pose a serious threat to ruling party leader and presidential hopeful Park Geun-hye. Since last year, many surveys have suggested Ahn could beat Park in a two-way race, shattering public perceptions widespread up until then that Park is on course to become Korea's first female president.

On Tuesday, the ruling party urged Ahn to clarify his position.

Ahn "should make his position official as early as possible and receive thorough vetting before the people," said Rep. Lee Hye-hoon of the ruling party during an interview with Yonhap News Agency. The lawmaker is one of Park's closest aides.

Lee urged Ahn to step forward and undergo public scrutiny if he aims for the highest office, saying voters need enough time to assess and examine his qualifications and it would be "impolite" for him not to provide the people with such chances.

"For example, we don't know whether he opposes or supports the Korea-U.S. FTA (free trade agreement), what stance he has on the naval base issue (on the island of Jeju) and what ideas he has on the issue of jobs for youth," Lee said. "He should put forth his stances on these big national issues."

The main opposition Democratic United Party (DUP) wants Ahn to join hands with it.

Acting DUP chairman Moon Sung-keun said Tuesday that Ahn should participate in his party's presidential primary, saying Ahn and the party both want to stop the ruling party from holding on to power.

Ahn is "a comrade in a broad sense and should hold hands with us and move forward," Moon said.

Should Ahn join the DUP, he would have to compete with the party's rising presidential hopeful Moon Jae-in. Moon, who served as chief of staff to late former President Roh Moo-hyun, was elected to the National Assembly in last week's parliamentary elections.

Ahn, a former medical doctor who gained fame in the 1990s after establishing the anti-virus software firm AhnLab, is widely popular, especially among young Koreans, due largely to his clean and upright image. He is now dean of the Graduate School of Convergence Science and Technology at Seoul National University.

His influence over voters was underlined during last year's Seoul mayoral by-election.

After Ahn suggested he might run, he immediately took an unrivaled lead in opinion polls. But he later decided not to run, saying he would instead back opposition hopeful Park Won-soon. Park, who had been a minor hopeful before receiving Ahn's support, won the election.

Analysts have said that Ahn's popularity illustrates the distrust South Koreans have in existing politicians and political parties, which have often come under fire for engaging in factional or partisan fighting without caring for ordinary people.

The public sees Ahn as a fresh alternative to the current political establishment, they say. (Yonhap)