In a 16-minute live video to his more than two million followers on Facebook, Salvini revealed that the "government contract" should be finalised on Wednesday, and railed against criticism of the deal in Europe and the media.
"We see the Financial Times write 'Rome opens its gates to the modern barbarians'," he said, referring to an FT headline from Monday.
"Better to be a barbarian than a slave that sells Italy's dignity, future, businesses and even its borders."
The "Contract for the Government of Change" being drafted by the League and Five Star was described as a "bomb" to the political order by Di Maio on Tuesday.
Both he and Salvini said that the final version of the accord and composition of the government team will be put to the parties' members for approval.
The agreement, a version of which was published on the Huffington Post website on Tuesday evening, initially proposed the introduction of measures to enable Italy's exit from the single currency, but both parties revealed that the idea had been subsequently removed from later versions.
However it does foresee the possibility of asking the European Central Back to write off 250 billion euros ($295 billion), or roughly 10 percent of Italy's debt with the institution.
EU Commission vice-president Jyrki Katainen had warned on Tuesday against the formation of a government that might disregard the terms of the EU's stability and growth pact.
Di Maio shrugged off such warnings as the protests of "Eurocrats that nobody elected", while on Wednesday Salvini, attacked EU commissioner Dimitris Avramopolous' request that Italy's new government not change its policy on migration.
"We heard some unelected commissioner say that Italy has to continue to do what it's always done, or rather -- pull its trousers down," he said.
Salvini said that the contract -- and an interior minister from the League -- would make sure that "only people with a right to enter Italy" would do so.
He said that cuts to the five billion euro budget for asylum infrastructure would be used to pay for expulsions of "thousands of criminals".
"A minister from the League who would work on security and border control would be a guarantor that whoever comes to Italy has the right to do so," he said.