Marco Polo Industrial Holding, a company created to facilitate the takeover and 65 percent owned by ChemChina, said its €15-a-share offer valuing Pirelli at €7.4 billion (US$8.4 billion) would be extended until October 27th.
Analysts said this would allow Marco Polo to secure the 90 percent stake it needs to take the group private and begin a complex restructuring which will see Pirelli split in two and its most profitable part eventually refloated on the Milan bourse.
The 35 percent of Marco Polo not held by ChemChina is owned by Camfin, a holding jointly controlled by Rosneft and Pirelli's CEO Marco Tronchetti.
The foreign takeover of such a famous emblem of Italian industry made waves when it was announced in March but the outcry subsided quickly with Tronchetti defending it as an option that secures the company's future and avoids the risk of a hostile takeover by a direct rival.
Under ChemChina's plans, Pirelli will be split into two units, one producing high-end tyres drawing on the company's experience in Formula One, the other industrial ones.
The new unit producing high-tech and racing tyres will remain in Italy with a view to being relisted in the future while the mass market production will be merged with ChemChina's tyremaker Aeolus.
The deal gives Pirelli an inroad into a Chinese market in which it previously had little presence.
In an interview with AFP in March Tronchetti said the takeover would have no impact on Pirelli's "crucial" involvement in motorsport and also reassured fans of its famous racy calendars that the annual collection of scantily clad supermodels shot by superstar photographers would continue.