Matteo Salvini, the leader of the League, and M5S counterpart Luigi Di Maio, worked over the weekend in Milan on a policy document called the contract for the government of change, in which they are expected to take a tougher approach towards illegal immigration and the EU. "We spoke about themes, not names", the League leader said, echoing comments from Di Maio before the talks started.
Around 70 days after the legislative elections that failed to produce a clear parliamentary majority, it would appear the League and the M5S have found some common ground to form the first anti-establishment government in Italy and western Europe. Despite aiming to present the results of their negotiations to President Sergio Mattarella on Sunday, no decision could be reached. For the composition of the government, the League and M5S must also agree on representation from the parties.
The Corriere Della Sera reported that a Milan court ordered the immediate "rehabilition" of Mr Berlusconi on Saturday, which "cancels all the effects" of his 2013 tax fraud conviction - including a ban on holding elected office. The Five Star leader indicated that the discussions may extend into next week. Salvini and Di Maio are also willing to make compromises over their flagship policies - the League's drastic drop in taxes and the M5S's universal basic income - which look tricky to reconcile in the eurozone's second most indebted country.
This might also benefit former prime minister Berlusconi.
Many investors are looking to Mattarella to be a stabilising influence on a populist administration amid concern about funding spending pledges and demands to review European Union treaties.
It means that Mr Berlusconi would be able to again run for prime minister if coalition negotiations fail and new elections are called.