The party also said that a meeting with the Shiv Sena will take place on Friday in Mumbai for the formal announcement.
Addressing the media at the residence of NCP supremo Sharad Pawar, former Maharashtra Chief Minister and senior Congress leader Prithviraj Chavan said: "Congress and NCP have completed discussions on all issues."
"There is a complete unanimity between the Congress and the NCP and we will move to Mumbai tomorrow and have a meeting with our pre-poll alliance partners. After that we will follow up that discussion together with the NCP and the Shiv Sena. As soon as discussions are completed, the media will be briefed about the structure of the proposed alliance," he added.
The remarks of the Congress leader came after parleys with the NCP in the national capital in last two days.
Earlier in the day, the Congress' top decision making body, the Congress Working Committee (CWC), met and gave a go ahead for the alliance with the Shiv Sena in Maharashtra, where the President's rule was imposed on November 12.
The Congress and the NCP on Thursday also held meetings separately of their respective leaders and then arrived at the residence of Pawar.
On Wednesday, the two parties held marathon meetings lasting over five hours to discuss the common minimum programme in the state.
The BJP and it's pre-poll alliance partner Shiv Sena contested October 21 assembly elections together and they won 105 and 56 seats respectively in the 288 member house.
The Congress and the NCP won 44 and 54 seats respectively in the assembly.
The Shiv Sena had a fallout with the BJP after Uddhav Thackarey demanded a rotational chief ministership, which was refued by the saffron party.
( With inputs from IANS )