Amid escalating tension and the turf war between the Centre and the Delhi government, Aam Aadmi Party (AAP), which has decided not to contest the Bihar Assembly elections, would offer tactical support to Nitish Kumar.

A senior AAP leader, requesting anonymity, said the party will campaign against the BJP and, if need arises, Delhi chief minister Arvind Kejriwal may also plunge into the battle.

"We have already made it clear that we are not contesting the Bihar polls, but we will certainly campaign against the BJP and tell people how the Narendra Modi government is not allowing us to work and creating impediments in the functioning of the Delhi government. If there is no truce in the ongoing war between the Centre and the Delhi government, then Arvind (Kejriwal) might undertake an extensive campaign against the BJP and Narendra Modi. Our party leaders and the state cadre will also involve themselves in the campaign," said the leader.

He said though AAP may not have a large support base in the state, it could put in jeopardy the fate of some BJP candidates.

"We may not be a reckoning force, but we certainly possess the capacity to influence 3-4 per cent of the voters. This could hurt the prospect of BJP, which is likely to contest the Bihar polls in Modi's name," he added.

BJP's defeat in Bihar, after the debacle in Delhi, would mean a loss of face for Modi. Elections to the state Assembly are likely in September-October.

Kejriwal shares a good equation with his Bihar counterpart. During the Lok Sabha polls JD(U) president Sharad Yadav had even campaigned for Kejriwal in Varanasi.

When asked whether AAP would publicly declare its support to Kumar, the leader replied, "We are going to campaign against Narendra Modi and the BJP."

The BJP and AAP have been locked in a bitter confrontation since the Lok Sabha polls. In the first round, Kejriwal took on Modi from Varanasi. Kejriwal was humbled by Modi and his party lost all seven Lok Sabha seats in the national capital to BJP.

However, Kejriwal's party exacted a sweet revenge in the Delhi Assembly polls in which it inflicted a crushing defeat on the BJP, which could win just three of the 70 seats.