SEOUL -- Han Duck-soo, South Korea's former prime minister, on Friday announced his presidential run after stepping down on the previous day.

Han told a televised press conference in the National Assembly that he will run for president in the June 3 election as he made up his mind to find what he can do for the future of the country, vowing all-out efforts to be selected by the people in the upcoming presidential election.

If elected president, Han said he would make all-out efforts to amend the constitution and hold parliamentary and presidential elections simultaneously in the third year of his five-year term in accordance with the new constitution.

Han pledged that he would immediately resign as president after the elections, indicating his willingness to shorten the five-year presidency to a three-year one.

The former prime minister, who had served as acting president following the removal of former President Yoon Suk-yeol from office over his botched martial law imposition, stepped down on Thursday.

Han has been one of the favored presidential hopefuls among conservative voters.

A recent survey showed Han garnered a support rate of 13 percent, surpassing approval scores of the conservative People Power Party's presidential contenders.

It was far below the 42 percent support for Lee Jae-myung, presidential candidate of the majority liberal Democratic Party.

The result was based on a poll of 1,000 voters conducted from Monday to Wednesday. It had a plus and minus 3.1 percentage points in margin of error with a 95 percent confidence level.