The government has already issued the financial targets that will provide the framework for the budget, drawing fire from the European Commission for plans to triple the previous fiscal deficit goal for 2019.
Ministers have said Brussels should reserve judgement until full details of the budget are unveiled.
"Next week, on Monday, the cabinet will approve the budget, which will then be sent to Brussels and to parliament," Di Maio, who leads the anti-establishment 5-Star Movement that governs with the right-wing League, said on Facebook.
Under Italian law, the government has until Oct. 20 to approve a budget and pass the bill to parliament for review. Both houses must then approve the package before the end of the year.
Di Maio's comments confirmed remarks made earlier on Thursday by 5-Star's Senate leader Stefano Patuanelli, who told reporters the government intended to approve the budget five days ahead of the deadline, as "a signal to Europe."
Economy Minister Giovanni Tria told a parliamentary commission on Wednesday that deficit spending would total 22 billion euros (£19.3 billion) next year, with the budget including 15 billion euros in cuts and extra revenue to help cover 37 billion in total additional spending.
(Reporting by Giuseppe Fonte and Gavin Jones ; writing by Crispian Balmer; editing by David Stamp)