ROME--Italian Prime Minister Mario Monti on Saturday announced plans to resign after pushing Italy's budget through parliament, a move aimed at staying above the political fray as the country enters a tense campaign season.

Mr. Monti's decision is likely to pave the way for Italy to hold elections as early as February, a month or so sooner than expected. Italy's 2013 budget is one of the few remaining items left on Mr. Monti's agenda, and parliament is likely to approve it by the end of the year.

Mr....