Sources said the move may materialise soon after Congress Vice President Rahul Gandhi arrives back from his visit abroad. Gandhi is likely to return to Delhi tomorrow.
Sources said Sidhu may join before the January 11 national convention convened by the party in the national capital to take forward its agitational programme against demonetisation and other "anti-public" policies of the Modi government.
Sidhu has already met Gandhi a few days ago and is likely to hold another meet with him before formally joining the party. He has also met with Punjab Congress chief Amarinder Singh last month.
Navjot Kaur Sidhu, the former BJP MLA from Amritsar East, has also stated that Sidhu may contest from her seat in the upcoming assembly polls in Punjab slated on February 4.
Sidhu has so far not opened his cards ever since he formed a front - "Awaaz-E-Punjab" with former Akali MLA Pargat Singh and Bains brothers from Ludhiana.
Pargat has since joined Congress along with Sidhu's wife, while the Bains brothers have aligned with AAP.