Congress chief Sonia Gandhi's lunch to opposition leaders in the Lok Sabha on Thursday is not so much about mouth-watering dishes, but making sure that both Samajwadi Party and Bahujan Samaj Party representatives attend it.

The lunch, in Parliament annexe, has been billed as a make-or-break chance for opposition unity to take on the ruling National Democratic Alliance at the Centre.

The Samajwadi Party of Uttar Pradesh Chief Minister Mulayam Singh Yadav and his predecessor Mayawati of the Bahujan Samaj Party are sworn political foes.

The Congress chief, therefore, has a tough proposition in persuading the representatives of these two parties to attend the lunch.

The SP leader in the Lok Sabha is Ramjilal Suman and Rashid Alvi is the BSP leader. So far, Congress leaders are tight-lipped about their guest-list.

Both Yadav and Mayawati have cautioned Gandhi to keep each other at arm's length in case she desires any sort of an electoral understanding with either of them.

In her press conference in Delhi on Monday, Mayawati likened both the BJP and Congress as Sarpanath and Nagnath.

However, the Congress leadership seemed to ignore the snub with party spokesman S Jaipal Reddy asserting: "The party chief's recent meeting with Mayawati was part of the process designed to unify the political strength of the secular parties."

Reddy asserted that Sonia's role in mobilising opposition unity to defeat the BJP-led NDA 'is our political duty to discharge'.

The Congress Working Committee recently resolved that it will not hesitate to enter into alliance with other parties at both the state and central levels.

Meanwhile, Kalyan Singh's return to the BJP fold on still being hailed by the leadership as a masterstroke.

BJP chief M Venkaiah Naidu made it clear the party will go alone in Uttar Pradesh and under Kalyan Singh's leadership.

The SP chief Yadav, who hid his disappointment at two ministers of Kalyan Singh's Rashtriya Kranti Party pulling out and handing in their resignations, put on a brave face.

He told reporters that the two RKP ministers Rajvir Singh and Kusum Rai's resignation would not affect his state government and that he still maintained cordial relations with Singh.

But pretensions apart, the SP chief has to ensure that the Muslim voters in UP exercise their franchise in his party's favour, something, which both the BSP and the Congress are aspiring for.

The Congress chief's unspoken worry is that even as the NDA appears to be resurgent, her own party is not free of dissidence.

In Kerala, the fight between Congress Chief Minister A K Antony and senior party gadfly Kannoth Karunakaran rages on with the continuing threat of a split in the state unit.

In Gujarat, rebel leader Shankersingh Vaghela, who snubbed Sonia by forming the lathi wielding Shakti Dal, is contemplating rejoining his former party -- the BJP.

In Punjab too hostility between Congress Chief Minister Captain Amarinder Singh and Deputy Chief Minister Rajinder Kaur Bhattal is simmering.