Five Star's leader Luigi di Maio said talks today had been "productive" and that negotiations were still ongoing over who will become prime minister.
A Five Star representative told AFP on Monday that the pair want to present the details of their agreement - including their prime ministerial candidate - to the president before making them public.More news: China's First Domestically Produced Aircraft Carrier Starts Sea Trials
Both ran for premier in March 4 elections for Parliament.
President Sergio Mattarella, who has the final word on nominating a premier, reminded the parties in a speech on Saturday that he is not obliged to accept their recommendation.More news: At least 61 dead in four states from dust storm
The partnership between Salvini and Di Maio would represent a blow to mainstream European political parties across the continent. These measures are likely to set Rome on a collision course with Brussels as the new government has vowed to ignore the budgetary restrictions now in place due to the Italian government's deficit.
A centre-right alliance led by Salvini's League won the most seats, while 5-Star emerged as easily the biggest single party.More news: Karnataka elections Siddaramaiah, Yeddyurappa rubbish hung house predictions
According to reports, the parties have agreed on rolling back increases to the age of retirement, while the M5S is willing to follow the League's hardline anti-immigration policies. Together they will be able to hold a majority in both houses. M5S is by far Italy's largest single party after conquering almost 33 percent of the electorate.