"The day after tomorrow I will submit my resignation to the president," Belka was quoted by the PAP news agency as saying.
On Thursday, Parliament will vote on a resolution to dissolve itself which, if passed, would lead to elections in June.
Belka's party, the Democratic Left Alliance, has suffered a huge drop in popularity since scoring 43 percent in elections in 2001.
The party's support now stands at less than 10 percent -- one factor influencing Belka's pledge to quit the party and join a new centrist grouping to fight the elections.
Belka has said he would stay on as caretaker prime minister, at least for a short time, if his resignation is not accepted by President Aleksander Kwasniewski.