West Bengal chief minister Mamata Banerjee announced on Friday a campaign to "free India of the BJP" in the 2019 general elections, seen as a move to unite the opposition and stem the rival party's push into her state.
She said her state would support any party that backs the oust-BJP campaign.
"The BJP has to be driven out of this country. Bengal will support any party that is opposed to the BJP," she said.
The eastern state remains one of the final frontiers for the BJP, which is in power at the Centre and rules 21 states. The Trinamool Congress accuses the BJP of trying to polarize voters on religious lines and gain popularity through a witch-hunt against the state's ruling
party.
Banerjee made a pitch for opposition unity, saying 18 parties supported non-BJP candidate Meira Kumar in the July 17 presidential election.
Bengal will stand with Sonia Gandhi, Lalu Prasad, Nitish Kumar, Arvind Kejriwal and all those who will oppose the BJP," she said.
The chief minister, who has opposed a range of central government policies, including the demonetisation drive and the goods and services tax, has blamed the BJP for the trouble in her state.
"Don't underestimate the Trinamool. I will see you till the end," she said at the annual martyrs day rally for 13 Youth Congress workers killed in police firing in 1993. At the time, she was a Youth Congress leader.