Minister Harin Fernando said he would retire from politics if the UNP decided against the presidential candidacy of Minister Sajith Premadasa.
Addressing an event in Kandy, Fernando said he would step from politics and spend five years "at home" if the UNP did not choose Premadasa as its Presidential candidate.
The Minister said Premadasa, a 52-year-old politician, is well-positioned to lead the country for at least another 20 years.
"He is comparatively young and energetic. He is a better choice in comparison to old and feeble candidates who are vying for the presidency," he added.
However, the UNP's Legal Secretary has made a formal announcement that it would be 'unconstitutional' to announce the candidate before the official declaration of the election.
The UNP has also pursued disciplinary action two ministers, Sujeewa Senansinghe and Ajith P Perera, who made critical remarks of the party leadership.