Salman Khurshid's comment comes in the backdrop of the opposition's efforts to stitch a united front.
Senior Congress leader Salman Khurshid feels it is difficult for the party to come to power on its own in the present situation, but opposition alliance must not be formed at the "cost of containing Congress".
The allies should also be ready to make sacrifices and adjustments for defeating the BJP in the 2019 general elections, he told PTI in an interview.
"All our leaders have made it very clear that an alliance (is needed) to change the country's government. BJP must go. Whatever it takes to sacrifice, adjust and negotiate to make the alliance a reality, Congress is willing to do.
"But it is only fair that it should be the same attitude of other (opposition) parties. The alliance must not be for containing Congress, the alliance must be for removing BJP and we are willing for anything," Mr Khurshid said
When asked whether it is possible for Congress to come to power on its own, the former external affairs minister said "it is obviously difficult today".
"If that is the objective (majority on its own) then we will have to work over a period of five years. Because you cannot work towards an alliance for three years and then suddenly say we will fight to win (on our own). You have to fight for five years. Today we are committed to the alliance and we will do our very best to ensure that the alliance succeeds," he said.
Congress is the only party that gets seats from all over the country and all other (opposition) parties get seats from their respective states, he said.
"Now the elasticity in numbers is much greater when you are talking of seats from all over the country and when you are talking of seats only from your state. This is the practical reality with which all the leaders have to deal with an open mind," Mr Khurshid, who also served as minister for law and justice in the UPA II, said.
Mr Khurshid's comment on the alliance comes in the backdrop of the opposition's efforts to stitch a united front against the BJP before the 2019 elections and BSP chief Mayawati's decision to go it alone in the upcoming assembly polls in Rajasthan, Madhya Pradesh and Chhattisgarh.
The Samajwadi Party has also decided not to forge an alliance with the Congress in Madhya Prdaesh, blaming it of being "non-committal for too long".
Mr Khurshid said the objective of the grand alliance is to defeat the PM Modi government.
"If the participants of the grand alliance forget this objective, then obviously it won't happen and it will be a loss for every party and the country," he said.
The Congress leader, however, sounded hopeful of getting Mayawati's BSP back in the fold, saying the issues in the assembly polls are different from those of the Lok Sabha polls.
"Once these five state elections give us some indications of what the public mood is, tying up the grand alliance may become easier," Mr Khurshid, who twice served as party president of Uttar Pradesh, said.
The post of prime minister won't be an issue in forging the grand alliance when opposition leaders have clearly said that the issue will be decided once the alliance win the election, he said.
"I think those who are raising this issue (prime ministership) do not want us to succeed against the BJP," he said.
While speaking on the revival of Congress, Mr Khurshid hailed party president Rahul Gandhi for "infusing fresh energy and determination" into the party and said it was a time for making sacrifices and give the best to the party.
"We lost some elections, but we won Punjab and kept the BJP away in Karnataka. In some places, we were ahead of BJP, but they misused power to form government...the upcoming elections in five states will be a measure of how much we have got back on our feet in the last four years," he said.
The former Union minister dismissed BJP's claim that the opposition alliance did not have a leader and said there were "leaders in the opposition alliance" along with four to five strong regional parties and that the "Congress even in its weak form is strong across the country".
About the foreign policy of the present dispensation, he said the PM Modi government had failed to build upon on what they had got from the previous governments and nothing much to show in terms of accomplishments.
Mr Khurshid rated the four-and-half-year-old PM Modi government as "disastrous" and said it had injected disharmony in the society.